It would have mattered. The Corwin amendment, which would have amended the Constitution, would only allow slavery where it currently existed. It banned slavery from expanding into new territories or states. That would actually have made things worse than they already were for the slave states, since up to that point the new states were allowed to decide for themselves whether to be slave or free.
The Corwin amendment was therefore a really bad deal for the slave states, and meant that they would eventually be outnumbered in Congress, and slavery would be abolished from the entire union by the eventual majority.
Which was all the slave-owning assholes wanted. They wanted it to never be taken away.
As a work-around, they wanted an equal number of slave states as expansion continued so they could prevent another amendment abolishing it later down the road.
I am not defending those fuckers for slavery or for it being the reason they seceded.
I am just making sure that nobody gets undue praise. The Civil War seriously changed the relationship between State and Union, or at least clarified it.
no slavery = no war is only true in that particular circumstance.
no slavery = no secession ever?
Way too presumptuous and unlikely in my opinion.