Well, if by "cash cow" you mean the south, you're correct. As I point out, the Union went to war to prevent secession.
But what prompted secession?
Slavery. Read what the founders of the Confederacy actually wrote &/or said.
Lincoln's greatness lies in saving the nation—though he did shepherd passage of the 13th amendment. It's pure fantasy to assume either Confederacy or Union would remain intact, without further instances of secession following.
I also believe in states' rights, separation of powers. But I don't believe in anarchy.