Doesn't mean the US was planning to invade Canada-it just means the military in times of peace keep themselves busy inventing all kinds of scenarios, I'm willing to bet there are military plans to deal with a zombie outbreak in some file.
The other thing is the military wants to cover themselves when political leaders ask for any contingency they can say they have a plan to deal with it-no matter how unlikely.
BTW to sidslotm, do find a more reputable site for historical research will you?