Caste is an excuse for humans to be selfish to anything they perceive as beneath themselves. That America has monetized it into competitive economics without morals was the full implementation of colonialism: extraction and accumulation toward the top of pyramid schemes without respect for the places or people that provide the resources.
Black people closest to the soil get the worst of it now with no defense. The violence flows downhill as the usefulness and wealth flow uphill.
It's not merely an American problem (though America clearly leads for now): it's humanity's arrogance about Life and merit fueled by blind beliefs and the sales of those blind beliefs; competition, money, power, imaginary beings and civilization itself (city walls isolating people from responsibility to the places they take from).