People from so many different countries come here to be a part of the american dream that a normal american wouldn't even have heard 'em during juniors. They are coming here because of the superlative opportunities which our economy provides which they will never there back from where they came.
We have university Engg/Docs/professors/economists/scientists from as varied country like Russia/Ukraine/Iran/India/Japan/ Korea/Turkey etc etc.
Most communities do preserve their distinct flavour to some extent but at the same time assimilate the ethos of our nation.
They bring with them a new dimension of thought process and diversity. We are an open society and we take pride in it.
That's what makes the U.S so powerful and always ahead of others in all fields. They attract/give equal opportunity to succeed to everyone irregardless of race.