I disagree that there’s a single culture associated with any race. Further, so do a great many black people. This is from 2007, so the percentages may be better or worse today, but obviously, there is no consensus among the black people: https://www.pewresearch.org/social-trends/2007/11/13/blacks-see-growing-values-gap-between-poor-and-middle-class/

I think African American is a useful term, within limits, because it recognizes that black Americans tend to be a mix of people from different places, just as white Americans are. Few families stay in the US for a few generations without becoming mutts.