So a few comments/observations from playing this game:
1) At this point, it seems likely the British will win this scenario. Not guaranteed, a lot will depend on if the rebels can hold onto Boston or Pittsburg, and keep a legit harbor open for when the French arrive. But I don't know the rebels can hold out to a multi-prong attack of the amount of troops the British have after 1776 reinforcements have arrived. 1777 is the British's high point, and the rebels low point, so its a bad time to be facing a consolidated push from the British. Which leads me to the next few points:
2) IMO, this 1775 scenario has a fatal unbalancing flaw, in allowing the British to immediately take Howe out of Boston on Turn 2, and send him anywhere. This allowed me to take Philadelphia very quickly, before the USA faction even has a chance to react (I've playtested it, there's nothing the rebel player can do to contest the landing if it's enacted immediately). New York is slightly iffier, but it's very easy to take as well in 1775. Losing Philadelphia in particular is devastating to the rebels, as some of their initial reinforcements come to this region, and immediately get stomped if its British held.
3) So, I think the scenario would be better balanced if the initial Boston fleets for the British either didn't show up until August or September 1775, or were fixed until this time. Howe's reinforcement army could be active, therefore leading to a historical Bunker Hill battle, or it could threaten more of Massachusetts if the patriots pull forces back from the siege, but it wouldn't be able to threaten the very exposed coastline anywhere at whim. And attempting a naval landing in fall/winter is a far riskier proposition for the British if they had to wait, particularly to September to do so (not to mention the patriots would have some reinforcements). This one change, IMO, would make the scenario largely balanced.
4) On a similar vein, being able to take Burgoyne's army anywhere when it arrives also makes things challenging for the USA (I had his forces in VA by June 1776). IIRC, the last time I played this,Burgoyne's forces showed up in Quebec, not at sea, but that was years ago and perhaps has changed since. If he were at Quebec, it would at least take longer before the British could sail him to the colonies proper, meaning he'd be less of a factor in 1776 and more of one in 1777. The British already get major reinforcements in 1776, having another 800-1000 CP stack is a bit too much on the already punished USA faction.
5) This game has reinforced my long held opinion the British have to consolidate to a single front, being split between North/South won't work. They really need to either focus on New England or the South first, so they can hold their rear areas with minimal forces and concentrate on one front. The USA faction, conversely, has to figure out how to keep the British from doing this. If the British go with a "South first" approach, the USA faction has to send forces south to contest it and make it difficult. In our game, had Washington been down in SC/NC, I don't think Cornwallis could've beaten him. I had about 600 CP in the area at its height, and had to detach forces to keep pro-rebel regions generating VP. I realize these comments are easier to say than implement, but nonetheless, I think taking Washington to the enemy, but keeping him moving light and nimble, never staying in one spot for long, is the best approach. I dread to think what would happen if there was a 800 CP quick-moving stack moving around SC or GA right now. Also, winning battles in the strategic and objective cities would help the USA get alignment loyalty back to pro-rebel alignment, which would really hurt me from a fog-of-war standpoint. If you can keep the British on their toes, running around all over the place, in 1776/1777, then once the French arrive in 1778 it becomes a whole lot easier. My biggest losses have come from attrition hits and epidemics, both of which hit me hardest when I'm moving forces around, if I were having to react all the time. And the British can ill-afford the losses, with their very limited replacements.
Anyway, it's a very interesting scenario, much like a boxing match of wearing your opponent out. I do think it's slightly broken in British favor, but this would be easily addressed by item #2. With that one small change, I think it'd be a very historical and tit-for-tat campaign.