In African and southeast Europe - and Asia - where slavery was far worse, existed centuries longer , and affected many more nationalities, there isn't this sort of extended grudge (for lack of a better word). The only discernable difference is they also don't have the Racism Industry we do, with CEOs like Sharpton, Jackson, et al who make their living at it.
Even in Africa, where there was not only commonplace slavery, but Africans enslaving and selling other Africans for profit, you do not see the sort of racism you see here. On top of that, the decendents of American slaves turn about and glorify their African brethren, whose ancestors sold theirs in the first place.
They need to get off the racist bandwagon and get a life.