Of course playing versus a human is much harder

but otherwise the rules are exactly the same...no cheating or AI boost in any way.
The best tactic is indeed small groups, provided you avoid battle except against the smallest British garrisons, by sneaking in from behind (use poor terrain such as swamps).
Keep one large army with most regulars and Washington as a force in waiting, ready to strike against medium size forces of the enemy. The group can keep hovering like in history in the Catskills / Hudson region... Threaten NYC, this is the city the Brits cannot afford to lose...
Another medium-large army can be a possibility, either in the Champlain or in Virginia.
Also quickly setup a task force with speedy units (Light inf) and fast-moving / ranger leaders to strike west...this will annoy the British and buy you some time...
IMHO, the British lost the war because of mere incompetence of their leadership... a competent human player will not make the same mistakes...so really playing the American side is a tough challenge...
