As it is, it’s too big.
Perhaps it could separate into independent countries (which would consist of groups of states).
California is already part of Mexico again.
The idea of secession will catch on when the leftist/socialist who live in the blue states think it is a good idea. Right now they are winning politically and forcing socialism on the unwashed red states. If they start to lose then they will want to carve off a piece of the USA to create their Socialist Utopia™. Nothing is a valid concept unless “they” think it is. So the trick here is to get the MSM and the establishment leftists to buy off on the idea - like it was their idea.