I believe that "natural" diversity is probbly fine.
In Switzerland I am not aware of conflicts between German, French and Italian speakers. I could be wrong.
Beyond that example,, there are many examples of conflicts, that last for generations to varying degrees.
To date the US exemplifies "diversity" that occurs over shared interests.
I believe that had been the hope in Germany, and Merkel now says it did not work.
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A demurral.
During the Chancellorship of Helmut Khol, the Berlin Wall collapsed.
To re-unite West w/East, he needed to invite Turkish labor to help re-build
the infrastructure of the latter, which the Soviets had allowed to deteriorate.
The Turks came w/the understanding that they were guests, not citizens,
they had to make an effort to assimilate and they should learn German.
If they were successful, they were permitted to formally apply for citizenship
at the end of their contract, as many successfully did.
An anecdote; several members of the German National Team that won two
of the latest World Cups, were the the sons of those laborers.
However successor Chancellors imposed no such conditions and terms on the
Muslims who immigrated and the results were as predictable as 2+2=4!!!!!
And Murkey is surprised?????