This is probably low probability, but is inspired by two things: 1) Turtledove's Marxist African-Americans, who did little other than suck and die, and 2) The Communist party of America's platform in the 1930s of supporting secession for the black belt, a region stretching from Louisiana into the Carolinas where blacks were the majority.
In OTL, there were also lots of ideas for a "black homeland" for freed slaves, all of which just happened to involve shipping them back to Africa. Is it possible to see a black homeland arising in the region? And what would it look like?
(Wow. That was incredibly vague, wasn't it?)