How does the South "win" the war?
What does the "win" entail?
When does the "win" occur?
What does the "winning" confederacy include?
You need some sort of foundation before any reasonable response can be offered.
Best,
Pretty much what he said.
Although, to be fair, the OP was asking something on the order of 'in all universes where the CSA succeeds, in what percentage does the Union force the CSA back into the fold?'
Which would be a reasonable question - if there were any kind of clue what PoDs would give rise to a CSA, etc.
Me, I suspect that the Union doesn't 'force' the CSA back into the fold, but that the CSA becomes a failed state, several states leave the Confederacy, and that several of THOSE rejoin the US.
Whether the Union tries to conquer the 'rump' CSA left after that (SC, GA and AL, maybe) is entirely open to question.
So... It boils down to what TFSmith says, actually, although in a more general sense. What range of PoDs let the CSA 'win', how likely are each, how would the world evolve in each, etc. Since that whole project would be worth multiple doctoral theses in Sociology and/or History, and no one would be convinced of the results, it end up not being a very useful question. IMO.