Chicago had huge, organized gangs. Until the FEDs targeted the leadership, and the centralized power bases in the projects got demolished.
Detroit has had, and I'm sure still do have huge drug gangs,
Some BLood sets in New York are REALLY organized,
The real issue isn't so much are black gangs organized, there have been countless examples of organized black gangs on a very high level, I think the real issue is diversification, and assimilation to legitimacy.
http://youtu.be/uwHUSQI4FOM
Check out this documentary if you want, about the GDs in Cabrini Green, CHuck Dorsey was a first cousin of mine...