Britain Declared War On Me Immediately as Upper Canada?

30 minutes into the game and I'm at a loss.

Playing as Upper Canada, I got immediately declared upon maybe 2 weeks after unpausing the game by Britain. Why? Their war goal is to annex me. I've done absolutely nothing aside from put three buildings in my construction queue and start a research. I'm still their puppet. I didn't change any game rules.

What is going on? How does this make sense?