Yes and no. There would be less to worktogether against, but now there has already been an example of collaborative bargaining working. It might fade for awhile, but it will come again and again. Indians holding lands that the colonists want? Breaking out across the Appalachians into the rich lands beyond? Defense with Spanish-incited indians in Florida and Louisiana? The after effects of those? These are all matters that the colonies are going to be concerned about, and the moment you have an assembly of NA, there's going to be horse trading for support here in exchange for support there. New York may not care much about Spanish Florida, but it does care about support to get into the Iriqouis Confederacy.That's right, but in OTL the pressure to cooperate was much higher - first, there was a war of independence to win (which also contributed to a feeling of shared interests) and even after that relationships with Britain remained hostile. In a TL where some kind of accomodation is reached, the pressure to unite against London would be much lower.
And this is the nature of all collective bargaining. But the thing is, even as people jump ranks occasionally, progress is made. The US Senate makes a good demonstration: each senator has the ability to stop all action unless overridden by a vast majority, and once a party beats that number it can freeze all business whenever it wants. But deals are constantly made, and though people disagree and have counter-interests, the legislation is still passed with a majority.That depends on how exactly the accomodation would look like that would be reached between London and the colonies. The more freedom it would give to the colonies and the less taxes it would demand, the less reason they would have to gang up against London. Also, even if there are things to bargain about, some colonies may be convinced that they could get a better deal for themselves by breaking rank with the others.
Actually, New England didn't sit out the war of 1812. There was anti-war sentiment embodied by the Copperheads (who still don't make up a majority of the politcos), but New England fought as much/more than the South. The invasion of Canada wasn't fought from Virgina or South Carolina, after all, and the National Anthem wasn't penned overlooking Charleston Harbor.Conversely, 90 years later the successor states to the colonies split into two factions and had a rather large war.
In 1812 New England sat out a war not to their advantage.
Even during the ARW the New England states sent virtually no aid to the South and a number of northerners were pushing for a 10 colony solution (leaving Georgia and the Carolinas to the British).
And of course, the ARW lack of aid was in no part due to how NE itself was constantly at threat by the British, who were qualitatively and quantitatively superior.
You're making a few leaps of faith here, mate. But as for the Civil War, that actually supports my point more than yours: a collective action by a group of states that didn't even outweigh the ruling force was able to throw its weight around for years before the first shell was fired. It was only when the fighting started that they were put down, but for decades beforehand the South had assumed a collective bargaining position despite ranging interests. Now remember that Britain would be the authority faction, and that colonies could find their own common causes despite ranging interests, and...
It's hardly "simple," because it's not "Us against Them." A legislature works by the members making deals and supporting eachother's proposals, a process called "logrolling" or "horsetrading" in the US. It's a natural process in Representation-based societies like NA was and is. You are, in effect, arguing against game theory here.The American colonies could react to legislation against them collectively in a collective manner (although they couldn't always manage that) but that simply means Britain has to avoid "Us against Them" creeping in.