Their monarchy was still a superpower back then.
Still, your Canadian friends probably needn't worry about an invasion of force coming from America.
They should be much more worried about the invasion of our culture and ideals, which is already turning their country inside out.
Which culture? The US is hardly homogeneous. They could use more our individualist libertarianism, and less progressive authoritarianism.
I was mostly referring to our culture of progressive authoritarianism, though our culture of entitlement is also a rot that tries to get out.