Canada is... not a normal place.Everything from its settlement patterns to its defense strategy to its national politics to its economic structure is wildly different not just from the United States, but from every other country on the globe. Until now that has not had an overly negative impact upon Canadian-American relations, but times are changing (and from the Canadian point of view, not for the better). To really understand recent shifts, we need to start not in Canada, but in Mexico.
It comes down to demography.