It is a job of a country's military to devise plans to attack other countries and how to defend from attack. I would imagine that Canada has a plan on how to invade the USA, no doubt labeled "Suicide 101".
No, actually after the manner of the reasoning in The Mouse That Roared, a Canadian invasion of the United States could be just what Canada needs: we'd set them back on their feet with foreign aid, rebuild their economy, . . .