NATO has over stepped its original mandate by a continent's breadth or two.   NATO is merely window dressing around American foreign policy to make it look like the US has broad international support. NATO provides valuable moral cover for American shenanigans, and if Mr trump wants to threaten its dissolution, that's fine with me. NATO doesn't do jack for Canada, our only real existential threat is from the South, the US. We'd be better off spending money on training and defense against a land invasion from our neighbors. The oceans protect us from Russia and China, who lack the blue water Navy and logistical support to actually invade North America.