They furiously foam at the mouth, saying Americans are natural multi-culturalists who relate to other American multi-culturalists, in the way that the French relate to the French.
It is culture, not race, that binds people.
However, some would argue that our major race (Caucasoid, Mongoloid, Negroid) does bind us in some way to more easily adapt to those sub-racial cultures, but those people are racialists, and are generally frowned upon by polite society.
And it does nothing in the way of explaining "white trash" who act a lot like "black people" from the "ghetto" ...just as an example.
Some people argue that our physical traits, though genetically minuscule in difference, really do affect things, though.
I try to keep an open mind about it, because I don't want to be the brainwashed liberal asshole who denied science.