The answer is that most people know there is no country in the world more accepting of strangers as is America. After three generations, people who have emigrated to Germany or France or Sweden do not feel -- and are not regarded as -- fully German, French or Swedish. Yet, anyone of any color from any country is regarded as American the moment he or she identifies as one. The country that the left routinely calls "xenophobic" and "racist" is in fact the least racist and xenophobic country in the world.
Given that it is the left and the institutions it dominates -- universities, media (other than talk radio in America) and unions -- that hate America, two questions remain: Why does the left hate America, and does the American left, too, hate America?
The answer to the first question is that America and especially the most hated parts of America -- conservatives, religious conservatives in particular -- are the greatest obstacles to leftist dominance. American success refutes the socialist ideals of the left; American use of force to vanquish evil refutes the left's pacifist tendencies; America is the last great country that believes in putting some murderers to death, something that is anathema to the left; when America is governed by conservatives, it uses the language of good and evil, language regarded by the left as "Manichean"; most Americans still believe in the Judeo-Christian value system, another target of the left because the left regards all religions as equally valid (or more to the point, equally foolish and dangerous) and regards God-based morality as the moral equivalent of alchemy.
It makes perfect sense that the left around the world loathes America. The final question, then, is whether this loathing of America is characteristic of the American left as well. The answer is that the American left hates the America that believes in American exceptionalism, is prepared to use force to fight what it deems as dangerous evil, affirms the Judeo-Christian value system, believes in the death penalty, supports male-female marriage, rejects big government, wants lower taxes, prefers free market to governmental solutions, etc. The American left, like the rest of the world's left, loathes that America.
So what America does the American left love? That is for those on the left to answer. But given their beliefs that America was founded by racists and slaveholders, that it is an imperialist nation, that 35 million Americans go hungry, that it invades countries for corporate profits, and that it is largely racist and xenophobic, it is a fair question.