It's not as hard as you appear to suggest...
If a self-identified Canadian opened a post by saying that he was exasperated with one of his/her politicians and solicited others' views, then THAT would be an invitation to pile onboard.
But a Canadian starting a post called "I'm so angry with the US (et al) government..." is rather presumptuous.
I think Canadians are decent folk.. they're good Allies, partners, and neighbors. Their political views usually align with mine too (social liberal, fiscal conservative).
I tried to nudge the discussion towards a more productive path by talking about the similarities of politicians the world over (they're of pretty low quality the world over, if you ask me). Tried that a second time by asking GO to reflect on how the Canadian PM has made things difficult on himself (I wasn't criticizing but reminding him of things that the Canadian press is saying ATM).
But nope! GO would rather stick with schooling those who would listen how much better the world might be if we all dumped our prez (which wouldn't bother me in the slightest) and amend our foreign policy in Canada's favor (again, don't have a big issue with that).
Friction arises, however, when he takes it upon himself (without benefit of citizenship) to offer such views uninvited. I wouldn't accept this behavior from a Canadian, just as I wouldn't accept it from a Russian (they tried that during the last election) or Chinese. Indeed, the fact he was a Canadian prompted me to start with the soft approach because, being congenial people, they deserve the courtesy.