Gwern argues here against supporting the American revolution.
It’s worth noting that a large part of the argument there (but far from all of it) would not apply to this question unless you were in such an influential position that you could have a meaningful effect on whether or not the war took place at all.
So I read Gwern and I also read this Dylan Matthews piece, I’m fairly convinced the revolution did not lead to the best outcomes for slaves and for indigenous people. I think there are two cruxes for believing that it would be possible to make this determination in real-time:
as Matthews points out, follow the preferences of slaves.
notice that a complaint in the declaration of independence was that the british wanted to citizenize indigenous people.
One of my core assumptions, which is up for debate, is that EAs ought to focus on outcomes for slaves and indigenous people more than the general case of outcomes.