Snake Featherston
Banned
Nothing is destined. The similarities and common roots of both the US and CS imply that they could get along after a fact. There are three nations inhabiting the North American continent and for all the conflicts in their shared past they get along fairly well
The idea of a continued conflict between the US and CS rests more with the chauvinistic view that United States is the end all and be all and anyone not wanting to be part of it is to be vilified.
No, it relies on the reality that the CSA would be hideously unstable and that if US towns on the border are getting raided by CS cavalry or "slave catchers" then there will be casus belli. The best case scenario in this kind of split is North Korea/South Korea with the Union as South Korea and the CSA as North Korea, dictatorial, isolationist, but a dystopian basketcase that doesn't bring problems elsewhere.
The CSA, rooted in holding one third of its population slaves for the benefit of a minority of the other two thirds, is built on a fundamentally unsound principle and the reality of their co-existence would be akin to India and Pakistan more than the USA and Canada. The idea that the CSA would last as a stable democracy tends to rely on fundamentally blinkered views of what the CSA actually was, though it could be for some time a stable dictatorship.