I think America is fine, and will be fine. We're big enough to absorb these immigrant communities even if some assimilate better than others.
I never understood the tolerance in the UK or France for these isolated immigrant communities. I mean you don't see millions of Frenchman living in enclaves in Vietnam, that sort of thing would not be tolerated. Vietnam is for the Vietnamese and their laws reflect that.
These countries, France, UK, others, have no historically been 'melting pots.' I don't know why they try to be, to their detriment.
In America it works because we have a fairly clear identity outlined in our Constitution. Ask me what it means to be an American and it's easy to say freedom of speech, press, free markets, bla bla bla.. ask a Frenchman what it means to be French and I imagine the answer is more abstract and hard to define
We have more than 50 million immigrants (legal and illegal) and their U.S.-born children (under 18) in the United States already, and it cost the country (tax paying citizenry) billions of dollars year just to allow them to exist here. We have some 25 million Americans out of work another 10 million or so that gave up and left the work force. This would suggest that the US is NOT big enough to absorb them not even big enough to absorb half of them!
That American identity is getting blurrier by the day with a political Left that thinks that Constitution is just a piece of paper and should be treated as such, a political Left that who's strength is growing exponentially in large part due to said mass immigration.