Every case is different and the UK as a political union without a written constitution can technically allow one of their four home nations to become independent (again).

The US has had bad experiences with seceding states. Big kerfuffle that people didn’t want to repeat.

When it comes to international recognition of seceding territories, it’s frankly a mess. And also, frankly, everything is possible. Kosovo is an example where the majority of the international community decided to recognize it as a sovereign country. It was a solution to a war situation that didn’t make all parties happy. Serbia and Russia, for instance, still don’t recognize it. So while Mass may not technically be allowed to leave, if it did anyway, it would depend on the reaction from the rest of the union first and foremost, and then on the international community. If they back you and maybe even send peace keepers, there is a chance still. But there is a whole laundry list of things that have to go right for this to happen.

I’d suggest you devote all your energy to fixing the United States first. Resist 47 and his GOP cult followers. Not all is lost just yet.