Like the rumored American Civil War game, this probably wouldn’t interest non-Americans much (but maybe you can get the Brits and French to play), but I think it’s a pretty cool idea.
For the powers, you could have:
1. Revolutionaries
2. Loyalists
3. British
4. French
and maybe Native Americans or Hessians as well.
You might run into trouble with the units… “Infantry, cavalry, or artillery? There’s too many choices!” (And Naval, but we all know there’s not gonna be a real battle for the Atlantic, until France enters the war on turn 15)
I’d opt for a A&A 1914 approach to the fighting, but maybe someone has a better idea.
Just my thoughts.