Only in poor, rural US areas where much of the population

No, the US was 90% white as recently as 1960. The North was always wealthier and whiter than the South was

Multiculturalism elsewhere in the world - especially in cosmopolitan areas - has been the norm since the big bang

Utter nonsense. Do you believe that ancient cities in England or France had millions of Africans living in them or something? Not to mention not even 10% of people lived in cities before the Industrial Revolution