You could see it as developed through diplomacy, but the reality was that the british colonies were all given responsible government _after_ the american revolution.

The unrests in Canada merely proved the point that the empire could not adequately control the colonies and they needed to become more self reliant.

This might sound generalist, but I don't think it's fair to look at America, Canada, Australia and New Zealand as separate reforms. They were all in the same empire that fell apart.

Anyway, I don't think there's ever diplomacy without at least _threat_ of violence.