Today, nearly all urban centers are governed by Democrats.  Some of those leaders are black.  Mostly, that governance has greatly failed African-Americans.  Nevertheless, blacks continually vote for that failed governance.  
African-Americans seem to want social integration and yet seem to also want to stay within the - largely unsafe  - confines of the urban village-ghetto.
You speak of hundreds of years of slavery and poverty taking their toll on black aspirations and accomplishment.  But you may be forgetting that for much of that long history, the majority of whites had it only marginally better.  Historians now tell us that 60-80% of whites coming to this country from 1620 and 1780 came as indentured servants - young people so poor and hapless that their own parents took them down to some English seaport and signed them over to a ship captain - trading seven years of  their young lives for boat passage to America.  They did that knowing they'd never see the boy or girl again.