What is the United States of America? Is it merely an accident of geography, or a job market for the world, or a multiethnic, multilingual lot of people who agreed (more or less, and probably temporarily) to live under a constitution? Those aren't goals to die for; yet many men for centuries have fought and died for America. Where did they get the courage, the stamina, and the perseverance to create and maintain America as an oasis of freedom and prosperity in a hostile world?

Patrick Buchanan believes that America is fundamentally a nation "held together by bonds of history and memory, tradition and custom, language and literature, birth and faith." Those bonds of brotherhood and ancestry existed before the U.S. Constitution was written, and sustained us through wars and economic depressions.

In his newest book, Buchanan challenges us to ponder our national identity, which already existed in the hearts of Americans when the Founding Fathers proclaimed the sovereignty of "we the people." Because we are now in critical danger of losing our identity, the apt title of his book is "State of Emergency: The Third World Invasion and Conquest of America" (Thomas Dunne Books: $25).

Buchanan rejects the notion that American identity is merely "creedal," i.e., united only by a common commitment to the U.S. Constitution and a set of basic laws. Even if that were true, it clearly would exclude the illegal aliens who violate our laws every day.

Buchanan agrees with Harvard professor Samuel Huntington that the "central issue of our time" is the migration into America of millions of people who come from very different cultures and refuse to adapt to ours. Buchanan calls the unprecedented entry of legal and illegal foreign born during the last 10 years a tsunami, unlike any wave ever seen in the history of the world.

The melting pot metaphor is a thing of the past. Today the United States is admitting people who don't want to be part of the nation called the United States; they want a land that looks like the United Nations General Assembly.

The immigrants who came from Europe in previous centuries fully assimilated, but many of today's immigrants instead are "self-segregating, forming their own towns within our cities, maintaining their language and identifying with one another, not America." They maintain their loyalty to their native land.

Is Western Europe a picture of America's future? Buchanan says that continent can now be called Eurabia because the civilization of Western Europe is fast folding under the dramatic fall in the native birth rate and entry of 20 million unassimilated Muslims.

Closer to home, Los Angeles may be a model of what America is to become. Sixty-one percent in the City of Angels speak a language other than English at home, which means they don't listen to English-language radio and TV programs, don't get their news from English-language newspapers and magazines, and don't share our heroes, history or holidays.

Those millions of migrants are putting on the chopping block our culture, including its morality, language, history, health, education, economic practices, and rule of law.

Many people dismissed the term "reconquista" as just the hysterical tirade of radical Mexicans, but Huntington warns us, "Demographically, socially, and culturally, the "reconquista" of the Southwest United States ... is well under way."

Mexicans have been taught that the United States "stole" the Southwest from Mexico. A 2002 Zogby poll found that 58 percent of Mexicans believe that the Southwest "belongs" to Mexico.

There was a time when our President, Theodore Roosevelt, could say: "There is no room in this country for hyphenated Americanism ... a hyphenated American is not an American at all.... The only man who is a good American is the man who is an American and nothing else."

Today, our elites celebrate diversity rather than U.S. ideals and identity. To justify the enormous numbers of foreign-born entering the United States, legally and illegally, we are reminded ad nauseam that we are a nation of immigrants.

However, immigrants, legal and illegal, don't come to America because of our diversity of residents, but because we are a land of freedom and opportunity. Most of the creators of our unique land were not immigrants.

Of the 56 signers of the Declaration of Independence, 48 were native-born Americans and two of the others came to this country as babies. Of the 39 signers of the U.S. Constitution, 32 were native-born Americans, and the few signers of both documents who were not native-born all came from Great Britain or British colonies.

The most diversity we had in the founding of America was that some came from big states like Massachusetts and some from small states like Delaware. "State of Emergency" lists all the obvious solutions: no amnesty, a border fence, eliminate birthright citizenship and taxpayer-paid social benefits, prohibit dual citizenship, require businesses to match employees' Social Security numbers, and time-out on legal immigration.

The book also contains all the facts about the failure of our government to stop the tsunami that has rolled over our country during the Bush presidency: the crime, the costs, the diseases, the drugs, the displacements. His book will convince you that we are, indeed, in a "State of Emergency."