I forgot about this. I should work on a TL involving it for later. Or work it into my current works somehow.
Will be difficult. A communist CSA is possible, but having it survive the inevitable US invasion will be near-impossible. I suspect the US would be a lot more angry/afraid at communists than it would normal Confederates. They'd view communism as much more of a threat.
Also- you'd need poor whites and poor blacks working together, otherwise the poor whites would lose.
If USA and CSA both go communist, they re-unify either by war or peacefully.