This is a meme that should die, because it isn't based in any fact, but is mere speculation. A quick look down any statistics for immigration (as other posters have pointed out) will show very little difference between the US and other "Western" countries. The assertion that multiculturalism restricts good governance clearly does not hold up to scrutiny. Canada, for example, compares well to Scandinavian countries on certain metrics (education, economy, formerly healthcare...), and nobody can plausibly argue that Canada is not at least as multi-ethnic as the US.