If they were fighting an entire campaign, The Marines could use their NVGs and engage at night, zero risk of injury. They could also sneak up to British barracks and put a little bit of C4 down the chimney
They could also chuck a grenade into gun-powder stock piles, set up minefields that would completely redirect enemy movements, lone marksmen can scout ahead, report back with radios, take out officers and run away, or put an AT-4 on the wagons carrying ammo.
When the soldiers hear about hundreds of men being slaughtered within minutes, they would lose faith in their officers and would just quit.
And if the Marines had artillery, ho boy. Brits would be sittin' in their farmhouse when incendiary shells come roaring through the ceiling.
Plus, back in the revolutionary days, the Geneva conventions/Ottowa Treaty/etc. didn't quite exist, so hollow-point bullets and trip-claymores are go.
Old muskets wouldn't do anything against modern body armor unless it was up close, in which case the Marines' superior hand-to-hand combat training would be of great use.