Seriously ... if Iran had 1000's of troops occupying Canada & Mexico and beating the drums of war ... how would we react?
We'd react by watching the drug cartels and cartelitos erase them off the face of the Earth. If the Mexican Army on home soil can't stop the Drug trade, do you think the cartels would let Iran come into their backyard and mulch a trillion dollar industry? And you realize that no one bothers to invade Canada right? That's why your question is so silly that it can't be bothered with a real answer. As far as invasion, we're pretty set, and willing to give Arizona away for the right price.