The deeper reason for this is because the population of slaveowners in the US were British culturally or ethnically, with a deeply empathetic and nurturing attitude to their slave populations. The Arabs in the middle east castrated them so they couldn't reproduce and the south american slave populations were brutalized to death much faster than they could be replaced by domestic births, while in the US slaves were treated like valuable livestock (and in many cases, held in the same regard as 'children' or 'invalids' that required care and supervision.) So much so that when the union freed them most returned to their home plantations.
The US/UK treated their slaves better, ended the global slave trade, and has spend countless lives and uncountable money on the welfare and uplifting of the negro race for hundreds of years. Every nigger in America should be thanking God Almighty their ancestors were shipped to these shores, but instead the ungrateful punks spend every waking moment hating. Fuck all of them, they dislike it so much they should all get dumped on the African coast.