Since the 1960s, America has been placing ever more of its chips on replacing its culture with one that--as soon as possible--has no dominant culture, in which its residents (legal and illegal) have primary identification with their own race, ethnicity, gender, religion, or sexual orientation.
I am certainly not enamored of some aspects of American culture, for example, its worship of materialism and of celebrity, the too-great disparity between rich and poor, its failure to provide an adequate health care safety net, and the liberal bias of its most influential media and colleges. But America has spawned a generally good quality of life for most Americans and produced a remarkable array of accomplishments from the car to the computer, from stents to Spielberg.
I am amazed that America is betting its entire future on multiculturalism. Yes, the U.S. could end up a dynamic place in which "diversity is our greatest strength," but multiculturalism could, instead, accelerate America's descent into third-world status. After all, not one of the world's 200+ countries is a clear multicultural success story. Diversity, far from a strength, seems, in every country including the U.S., to perennially be more a source of strife than of strength.
Yet, without firing a shot, identity groups within the U.S. are replacing American culture with some yet evolving mixture in which pluribus drowns out unum, in which what's good for America (let alone the world) is replaced with what's good for Latinos, women, Blacks, fundamentalist Christians, etc.
As the decades go on, would you bet that most Americans will find the U.S. a more pleasant or less pleasant place to live? A more productive or less productive country? I'm not sure, but I am certain that we don't have sufficient basis for betting the whole country's future on multiculturalism.