I don't know what you're trying to say. Is it not true that the whole reason black people are even in the US is because of colonization? The aftereffects of enslaving a race of people on such a large scale will naturally reverberate throughout history. One of the justifications for slavery in the first place included dehumanization.
And remember, the civil rights era began only 50 years ago. By contrast, Jim Crow -- institutionalized, legally-sanctioned racism -- was the law of the land for 100 years prior. No matter how far we've come, that can and still does leave an impression. A case in point would be Lee Atwater's Southern Strategy; a major party's electoral strategy more or less explicitly hinged on exploiting racism. Or lookup sundown towns.
So what's the problem? It seems perfectly logical and uncontroversial to suggest that the US citizenry, including black people, would still have widespread problems with race, subtle or overt. But on account of the (usually) social rejection of overt racism, people tend to think racism is over. It's pretty straightforward.