Yes, Canada and the US have fought at the beginning of the American Revolutionary War at the time when colonial troops marched all the way to Quebec City before being repelled, then when 1812 war occurred, the so-called “war hawk” members of Congress wanted to make a second go-around and also there were an opinions for invading part or all of Canada which was a British colony, but all these fightings finished in 1814 and from this time USA and Canada became strong allies.