
I mean it’s not like the imperial powers of Europe wouldn’t have been doing that shit without America being independent. I think it’s most valid to consider this in the context of native Americans because that’s something Britain was actually better on, and slavery because Britain did abolish slavery before the southern USA but after the northern USA.
There might be further positive effects. Had liberal nationalism not emerged in Europe, Italy might not have unified, and fascism might not originate. But the monarchies would retain power for longer. I believe we would still see conflicts between monarchical powers, and they, like any other powers, would develop more powerful weapons. Perhaps with less ethnonationalism there is less genocide in Europe, or it could continue to occur in the colonial periphery, or it happens anyways.