Historically a conquering people often treat the vanquished poorly(see for example the Spartans and the Helots.) Whites will get used to poor treatment as time goes by.
A nation with many distinct cultures - and no desires to assimilate - usually falls apart. The breakup could be peaceful (like with the Soviet Union), a bit messy (Yugoslavia), or very messy (the partition of India).
I wonder which of these will be the fate of the USA.