Yes it does matter because by succeeding they broke the US Constitution, and by attacking the US military they committed an act of war against the United States military. Your comparison to the current situation in Venezuela doesn't hold because the US Civil War wasn't a foreign intervention, it was a domestic constitutional conflict.

Ok! Imagine the North was the one to fire the first shot to end slavery. In a hypothetical different timeline. Apparently you would oppose this and would just support letting slavery exist indefinitely in the south?

the south was already signed onto the law for ending slavery, and were part of the same union.

you havent made a good enough hypothetical yet.

there's no lack of slave states around, including ones that the US does business with happily. i think yes, if you made your hypothetical "what if the US had a slaver neighbor" yes, the US would be leaving them alone, other than some economic pressures here and there

There is not one word in the US constitution that bans secession.