Playing as Great Britain, I managed to form the Thirteen Colonies in North America relatively early. With my permanent casus belli against primitives and superior military technology, I quickly subjugated several native tribes. Their provinces became a part of the Thirteen Colonies, and I was pleased to watch my subject grow and prosper.
...A few months later I noticed large rebel stacks in all of the recently conquered provinces, which eventually broke the nation, freed the tribes, and generally undid all my hard work. Turns out, I'd conquered too much, too quickly and the Thirteen Colonies, with over 100% overextension, had triggered some rather nasty events.
In future, it would be useful to know the overextension of my subjects ahead of time, so I know whether I should be going to war, or giving them some time to core their newfound holdings.
Is there a way to check the overextension of my subject nations?