We had more "weapons" n the revolution than just the musket, they weren't all "guns" but we had them. They could focus not on a fast paced action 2st person shooter, but maybe a action game that has you using blunt weapons a lot and melee combat more than using the gun. It could be done, very well in fact, if a competent developer handled it. I think the problem lies more in, America isn't so popular right now so nobody thinks a game about our beginnings would sell to non-Americans. It likely won't happen ever but I think it could and would be cool.
Out side of WWII, the futuristic setting is the only other option it seams. How about something like Heretic, a Fantasy FPS that uses Magic instead of weapons?