A good question, but I view the circumstances between the 2 wars a bit differently. The British were a LONG ways away as a nation, and they had a sea to contend with to plan on troop movements. And then you have the French sympathizing with the colonies, and HATING the British...
The south was up against a more modernized foe, with a well established transportation system in place, and a LOT more folk to pull from…all this with the North smacked right up beside the South.
Sherman said it this way…”You are rushing into a war with one of the most powerful, ingeniously mechanical and determined people on earth-right at your doors”
I will not blame the South for wanting to break off with the North, but their timing/lack of long range planning could not have been worst!