Yeah. ;-) You and a lot of others.

Militarily speaking, we are a minor satellite of the USA. We don't need a very big armed forces, as you say, because of our geographical position. The only nation which can do a land invasion of Canada in any practical sense, is the USA (I don't envision the Russians trying to send an army across the North Pole. ;-) The USA tried invading Canada once, back in 1812-1814, but they weren't a superpower then, and Britain was, so we stopped them. There would be no way of stopping them if they tried again in modern times, but there would be guerilla warfare just about forever, I expect, until the occupying forces left.

However, I think there is little danger of that happening in the forseeable future. It's much more profitable for both of us just to do business as usual...and the USA can get what it wants through economic pressure on Canada.