In fairness, it seems we're in agreement - slavery was not the raison d'etre of the CSA - there were several reasons for its existence - one of which was slavery.
I don't like answering what ifs, as there are usually too many variables. If slavery had never existed, North America, and indeed the whole world, would have been very different places by 1860. However, if everything else smoehow stayed exactly the same, and the exact same pre-war conditions existed - in my opinion war was still likely. When two economic interests compete fpor political power, war is always likely.
So if Cork fans like to fly the Confederate Flag because of it's lovely red colours, why don't we see any of the red Nazi flags at Cork matches? It's a lovely looking flag.