This is rather fun because Francis' arguments are so silly. "Grim existential challenges"? She had to invent some for the occasion. (Boo! the Chinese!) Canada is already under the U.S. security umbrella in every way that matters. As for how similar the two nations are (if you don't count French Canada), sure, and http://en.wikipedia.org/wiki/Narcissism_of_small_differences.

I live in what is arguably the most Americany of Canadian cities, and even here this idea isn't even a fringe position. I vaguely remember hearing years ago that some people had once proposed it, but it wasn't considered polite to mention who they were. If it ever turned into a political movement in Canada it would meet with overwhelming resistance. It's an identity thing.