Also, and I don't know why I didn't think of this sooner, they tried combining the precise area into a single polity before in OTL. The Dominion of New England existed for all of three years before it tore itself apart because people from the constituent parts couldn't get along. Throughout colonial history, there have been points where the New England colonies have been willing to go to war with New York and Pennsylvania, most recently during the 1780s. When you have two parts of a single commonwealth that are willing to go to war with one another, or have a history of doing so, you've got yourself a recipe for disaster.
Yes, because if it didn't work in the 1780, it most certainly won't work in 1991. I'll just go ahead and tell the French that their whole concept of republicanism will just fail in the end.