Doesn't this trend manifest in European countries as well? (E.g. https://www.jrf.org.uk/report/poverty-rates-among-ethnic-gro...). I don't know about equality, but correlation seems to be there and doesn't strike me as intuitively "weird," or surprising, if undesirable.

Now the linkage in the zeitgeist of race and socioeconomics is another matter. I'd be curious if it can be attributed convincingly to some American social factor (racial heterogeneity, our media, our relative lack of ethnically meaningful home states), but that's one for the social historians.