Today's challenge is I think, an interesting one. In today's challenge, there has already been a POD. The CSA has managed to win it's independence, the means isn't necessarily important, but if you need to use whatever would be the most realistic means of the CSA achieving such.
Anywho, your challenge, should you accept it, is to have the CSA before or after 1900 to become a Communist state dominated by its black population. Bonus points if you can come up with a legitimate good reason that the US does not intervene, and bonus points if this Communist CSA forms its own variant of communism, rather than some sort of copy-pasta of Leninism/Stalinism/Maoism etc.