So natural segregation is actually good and problems start when we all try to become alike.'Assimilation' is never absolute or immediate.
'National culture' is changed by the very people who are expected to 'assimilate'---by the time 'they' assimilate, they often have changed the culture into which they assimilate.
I generally discount claims of American exceptionalism. But in terms of diversity of religion, race, and ethnicity, I'll hold that the US is exceptional when compared to the history and development of European nations, and we've always been better for it. Why change now? Everyone knows a mutt is healthier than a purebred (speaking in terms of culture, not genetics).
Do I really care about a German's views of race, ethnicity, and national character? Pass, for obvs reasons.
Not afraid to admit my bias here, as someone who married a daughter of immigrants.
There's no such thing as natural segregation and, yes, everyone becoming alike is less-than ideal. The US is remarkable in having political institutions that were created to accept and manage diversity. That which many today implore newcomers to 'assimilate' into is an amalgamation of religious, cultural, racial, and ethnic traditions. Multiculturalism and diversity have been (usually) mainstream American virtues since the colonial period (certainly in terms of rhetoric, at least). If anyone is proud of our national heritage---ironically one of the foundations of anti-fascism, Frau Merkel--then I'm not sure why this would be such a crisis now.So natural segregation is actually good and problems start when we all try to become alike.