Wait so nations don't want land that once belonged to them back if its stolen from them, as this would require the UK to have intervened, andit would be seen as only a victory of the UK? So the world wouldn't be dappled by mass slavery unlike how it was in history? Also the AMerican party system would change as a result of this conflict. Also you seem to be ignoring Ameircas already present tendency to see itself as the greatest nation on earth. It wil want to eliminate that which counters that narrative that being the CSA and if the CSA acts as a imperialist slave spreading warmonger like you say it will certainly get alot of support to do that. I mean I will say you've eliminated southern culture so less support of oligarchy in the late 20th century now, and no lost cause. So you have created a slightly better world.