The OTL Civil War pretty much exhausted the South. It'll take more than a generation to recover, meanwhile the North is booming making it even more stronger than in 1860. At best, if it involves the South, any so-called Civil War Mk II will be more like an isolated uprising, here or there, which won't last very long.
However, it doesn't have to be a North vs South re-run, but at some point in time there could be a North-East vs Western States Civil War for various reasons - especially as California grows in strength & influence, whilst Washington DC pretty much ignores whatever is going on west of the Mississippi (apart from dealing with Indians). So as relations between East & West deteriorate, to the point of open conflict, the South declares neutrality on the matter, sits back, watches the Civil War Mk II play out, then takes advantage on whatever maybe on offer after the Second Civil War.