It would be nice if there was a means for people to choose divisibility, at least.
From that perspective only, I think the south might have had the better of the argument. That the region should have been capable of leaving the union.
From other perspectives (eg black people were not able to vote, slavery etc) things look very different, obviously.
Regional referenda make possible a peaceful process, whereas indivisibility means it takes a civil war to resolve certain differences, which is a terrible way to do things.