Anyone worried about an erosion of America's global status might consider this modest fact: Facebook is the dominant social network in Mongolia.
Along with its pervasive social media, the United States leads in myriad other ways _ from the allure of its movies and music to the reach of its military. It's tough to match a nation that deploys troops to Australia and central Africa, propels Beyonce to global stardom, and produced the Twitter-style technologies that abetted the Arab Spring.
"American entrepreneurs are defining the digital age," said Harald Leibrecht, the German government's coordinator for U.S. relations. "And when looking for the `next big thing,' we very much expect it to come from over the Atlantic as well."
So what's with all the talk about America in decline? There seems to be a forest's worth of recent books raising that possibility, with gloomy titles such as "That Used to be Us." Republican presidential candidate Mitt Romney suggested that President Barack Obama considers the U.S. "just another nation."
Abroad, foreign policy experts are following this discussion with a mix of bemusement and concern. A dozen of them, in nine countries on five continents, shared their thoughts with The Associated Press _ agreeing that the U.S. stands alone as a global superpower, yet perceiving an array of weaknesses that could undermine its stature as numerous emerging powers seek a bigger role on the world stage.
Cited most often: the partisan political gridlock in Washington _ viewed as hindering efforts to tackle other long-term problems.
"Some U.S. vulnerabilities are quite obvious," said Dmitri Trenin, a Russian expert on diplomatic and security policy, in an e-mail from Moscow. "The issue of debt ... too loose financial regulation, social inequality which is punishing America's middle class."
Trenin, director of the Carnegie Moscow Center, predicted the U.S. will nonetheless remain pre-eminent for decades, yet questioned the ability of America's political elite to interpret and respond wisely to global developments.
"This is not always impressive, and some comments made on the election stump are downright depressing," he said.
Narushige Michishita, a professor at Tokyo's National Graduate Institute for Policy Studies and adviser to Japan's government on security issues, views the debate in the U.S. over its global stature as a sign of insecurity. He says it has prompted to Japan to look to other strategic partners to bolster its position in Asia.
"It is clear in relative terms that the U.S. is starting to decline in comparison with China," said Michishita. "As U.S. commitment and influence starts to decline ... it is inevitable China will expand."
China, for all its size and rapid economic growth, is decades away from any plausible claim to equal stature. The U.S. dollar is still the world reserve currency of choice, and America will have far higher per capita income even when China _ with more than four times as many people _ eventually claims the world's largest economy.
Nonetheless, the latest global attitudes survey by the Pew Research Center, conducted last year, found that a majority of respondents in 15 of 22 nations believed China either will replace or already has replaced U.S. as the leading superpower. This view was especially prevalent in Western Europe _ for example, held by 72 percent of French people.
Among Americans, the percentage saying that China will eventually overshadow or has already overshadowed the U.S. increased from 33 percent in 2009 to 46 percent in 2011.
What do China's experts say? The Chinese Academy of Social Science's Comprehensive National Power index _ which weighs natural resources, population demographics, and military, scientific and economic strength _ ranks the U.S. first and China at No. 7.
By some other measures, China fares worse _ it places 101st in the United Nations' latest Human Development Index ranking countries according to life expectancy, educational attainment and income. The U.S. placed fourth after Norway, Australia and the Netherlands.
To some in China, the self-doubts in the U.S. seem overblown.
"The U.S. has a strong sense of crisis," said Zhu Feng, an international affairs expert at Peking University who frequently travels to the U.S.
Zhu's advice, when it comes to talk of China surpassing the U.S.: Don't believe the hype. By almost every measure, he notes, China still lags behind. It is investing billions in cutting-edge research, yet innovative spirit may at times be restrained by an oppressive political climate and a culture which values hierarchy and conformity.
"China is an adolescent power," Zhu said. "The most important lesson is to learn how to be a great power."
The United States has spent much of its existence learning how to be a great power _ culminating with the post-Cold War era in which no single nation could rival it.
Yet the Republican presidential candidates often criticize Obama for what they perceive as a reluctance to embrace America's uniqueness.
One comment they seized on: Obama saying he believed in American exceptionalism, "just as I suspect that the Brits believe in British exceptionalism and the Greeks believe in Greek exceptionalism."
Another challenged remark, regarding the need to invest in infrastructure:
"We used to have the best stuff. Anybody been to Beijing Airport lately?" Obama said. "Well, we've lost our ambition, our imagination, and our willingness to do the things that built the Golden Gate Bridge and Hoover Dam."
Said Romney, during a campaign debate, "We have a president right now who thinks America's just another nation." GOP rival Newt Gingrich, author of a book titled "A Nation Like No Other," has made American exceptionalism a centerpiece of his campaign.
Obama has been blunt in rebuttal.
"Anyone who tells you that America is in decline or that our influence has waned, doesn't know what they're talking about," he said in his State of the Union speech.
The polemics have had a stimulus effect on at least one economic sector _ a booming mini-industry of books engaging in the debate.
The titles often tell the tale: "The Post-American World" by journalist Fareed Zakaria; "That Used to Be Us" by New York Times columnist Thomas Friedman and foreign policy professor Michael Mandelbaum; "No One's World" by international affairs expert Charles Kupchan.
Friedman and Mandelbaum argue that the U.S. can recover its greatness, but only by aggressively tackling such challenges as globalization, budget deficits and excessive energy consumption.
Kupchan, a Georgetown University professor, argues that the dominance of the U.S. _ and the West as a whole _ is weakening in tandem with the rise of China, India, Brazil and other emerging powers.
"We're headed to a world for the first time in history that will be interdependent, globalized but without a political anchor," Kupchan told Book TV. "Most of the 21st century won't have a dominant player."
Even within the U.S. government, there's acknowledgment that America risks losing its edge in some sectors.
A Commerce Department report released in January said the economy's scientific and technological foundations have been eroding at a time when many other nations are growing stronger.
"In short, some elements of the U.S. economy are losing their competitive edge, which may mean that future generations of Americans will not enjoy a higher standard of living than is enjoyed in the United States today," the report warned.
The U.S. education system is slipping in some areas, such as students' training in math and science, according to the report. It said the U.S. is "lagging behind" in some vital aspects of 21st century infrastructure, such as broadband Internet access.
Another somber assessment came from a task force formed by the American Political Science Association _ it concluded that America's global stature had "declined dramatically" over the past decade.
The task force chairman, Professor Jeffrey Legro of University of Virginia, said U.S. policymakers need to rethink budgetary priorities.
"All our money is going into entitlements," said Legro. "We need a rediversion of money into other areas _ things that provide for the future, not for the past."
Across the U.S. border in Canada, Carleton University foreign policy professor Michael Hart has been keeping watch on the fiscal impasse in Washington.
"Obviously the U.S. is very divided on some very big policy issues, and that has some impact on its ability to exercise leadership in the rest of the world," he said. "It undermines confidence that others have."
As a Canadian, Hart has a close-up perspective on other U.S. strengths and weaknesses. America's health care system, for example, lacks the universal coverage that Canada and Western Europe offer, yet it remains a global role model for quality of care at the top end of the scale.
"If you're going to be sick and you can afford it, the U.S. is the place to be _ for speed, for thoroughness," Hart said. "In Canada, you have to wait. The best thing to do is call an ambulance, even if you don't need one _ it moves you up the queue."
Hart sees a similar dynamic with education, suggesting that Canada has more equitable outcomes for its K-through-12 students yet lacks any universities on par with the America's best.
Among America's other hemispheric neighbors, Brazil stands out with its booming economy, and its upcoming roles as host of the soccer World Cup and Summer Olympics.
Alexandre Fortes, a Brazilian labor historian currently at Duke University as a visiting professor, said there is some uncertainty among his compatriots as to how eagerly the U.S. will support Brazil's ascension.
"A lot depends on the U.S. learning that other countries have the right to follow their own path to development _ and sometimes that may produce short-term conflict with U.S. interests," Fortes said.
On his recent U.S. visits, Fortes has detected increasing inequality, political polarization and anxiety about the future.
"If the U.S. doesn't get back its capacity to fulfill the American dream on a more inclusive basis, it won't get back to playing a leading role, in a more positive way, globally." he said. "I still think the U.S. will be the dominant power for a long time ... But which kind of future is it going to offer its own citizens in terms of social inclusiveness, good education, good health care?"
Aloisio Araujo, an economist at the Fundacao Getulio Vargas in Rio de Janeiro, noted that China is an increasingly important trade partner for Latin America.
"But in terms of values, and so many other dimensions, the United States is still the natural leader and will be for many decades to come," he said.
In India, another emerging power, there's less awe of the U.S. than in the past, according to economist Rajiv Kumar of the Federation of Indian Chambers of Commerce and Industry.
"The U.S. star is seen to be falling not because the U.S. is weaker, but because there are other stars that are starting to shine," he said.
America remains the strongest country, "but there's no need to say it," Kumar said. "In fact, insisting on it is counterproductive."
In February, Kumar and other foreign policy experts released a report arguing that India should maintain its philosophy of nonalignment, which it held throughout the Cold War, while tracking how U.S.-Chinese relations evolve.
"Why should India align with either one of them?" Kumar asked. "They're like two drunken sailors leaning against the same lamppost... You don't know if you should join them, help one or the other, or just stay out of the way."
Across much of South Asia and the Middle East, views of the United States are colored by its military struggles in Iraq and Afghanistan, says Kamran Bokhari, a Toronto-based analyst who often travels to the region for his work with the global intelligence company Stratfor.
"I get the sense that elites in that region think the days when the U.S. could impose itself and its policies are a thing of the past," Bokhari said.
"They look at the past 10 years _ all this time the U.S. was obsessed with al-Qaida while in fact the Arab world was moving in a completely different direction. This unrest (the Arab Spring) didn't come out of nowhere, and yet the U.S. dismissed it."
On the cultural front, in contrast, the U.S. remains an unrivaled powerhouse _ movies, pop music, TV shows enjoy vast popularity.
The founder of South Africa's annual Cape Town Jazz Festival, Rashid Lombard, devotes half the showtime to African performers, the rest to international musicians. And every year, he says, "the U.S. is way ahead."
It's not just the artists; Lombard hails the American institutions that groom and showcase talent. He directs students to the Boston's Berklee College of Music, hopes to develop a partnership with Lincoln Center, and arranges for Cape Town music students to work via video link with students at The Juilliard School in New York.
If artists around the world are catching up, it's because of American generosity, Lombard said. "So much has been shared with the rest of the world."
Among America's longtime trans-Atlantic partners, the dominant policy concern for now is the European Union's tumultuous debt crisis, yet there's also apprehension that the U.S. might scale back its global role in ways that could impact Europe.
Alexandra de Hoop Scheffer, a professor at the Institute of Political Studies in Paris and director of the Paris office of the U.S.-based German Marshall Fund, said she and her peers were struck by the U.S. decision to pass up a dominating role last year in NATO's military intervention in Libya.
One result, she said, is uncertainty about who in the West will assert leadership in future crises.
"We understand that the United States is going through difficult economic period. We are, too," she said. "We're in a strange transitional time, where both sides of the Atlantic are expecting the other side to take more responsibility and leadership on the international scene."
In Germany, foreign policy expert Josef Braml has joined the publishing boomlet with a new book titled, "The American Patient: What the Looming Collapse of the USA Means to the World."
Braml, who analyses the U.S. for the German Council on Foreign Relations, says America is not on the brink of a free fall, but needs to break its political deadlock to grapple with problems in education, energy policy and other sectors.
"Deep down, Americans know that they have huge economic problems," Braml said. "They are not so sure if their children are better off than themselves ... Some people already talk of a lost generation."
He also said America's ventures in the Middle East had tarnished its image as a bastion of human rights through its support of authoritarian regimes and its sometimes harsh treatment of detainees.
"Europe still sees the U.S. as a world leader, and doesn't want to see that America is getting a lot weaker," Braml said. "Maybe we don't want to see it because that means we need to jump in."
Harald Leibrecht, a member of Germany's parliament as well as the government's coordinator for U.S. relations, agrees with Braml that America is in a funk.
"Traveling in the U.S. these days, one gets the impression that the famous American optimism and the irrepressible belief in the promises of the American dream _ characteristics for which we Germans have always greatly admired the Americans _ have taken quite a knock recently," he said.
But he expects a rebound.
"Throughout its existence the U.S. has always reinvented itself and gotten out of a crisis stronger and better than before," Leibrecht said. "I deeply believe it will be exactly the same this time."
Associated Press writers Charles Hutzler in Beijing, Eric Talmadge in Tokyo, Donna Bryson in Johannesburg, David Rising in Berlin and Katy Daigle in New Delhi contributed to this report.
David Crary can be followed on Twitter at http://twitter.com/CraryAP