And we've lost, twice! (American Revolutionary War and War of 1812)
Third time is the charm?
It would not be nearly as straight forward as "America military is big and grunts loud, Canada has beavers and mittens."
I can't tell if you're serious or not.
It's ridiculous on so many different levels, and that seems worth considering.
Plus, when such large portions of the economy are exporting culture and currency, the US is basically in the business of selling cooperation. So that would fall apart pretty quickly, and with it the immigration the sustains population despite low fertility rates.
Plus it's just inconceivable that it would be a goal in the US. Maybe that's just good propaganda, but I think not.
The event is a bit forgotten in the US but here in Canada, it's taught in high school. The relatively huge celebrations of the 200th year anniversary of the 1812 War back in 2012 also mentioned the invasion quite a bit.
However, the loss of the American colonies led to an increased British military presence in Canada (1 soldier for every 5000 settlers) which made rebellion practically impossible.
One rebellion led to the hanging of all the leaders and they never attempted to revolt again. Since then, they've been brainwashed into thinking this was best for them and that Americans are a bunch of unrestrained morons.