Of course it is. Troops would just be moved to “temporarily” occupy shit we want. (Or move to liberate Alberta.) Hell, you could probably do it with ICE agents.
> Any attempt to do so would trigger a civil war within the US
You’d take up arms against the U.S. because it invaded Canada?
Of course you wouldn’t. Neither would others. It would be brushed way as an another atrocity.
> 300,000 poorly trained reservists aren't going to seriously change the calculus
It’s people you have to shoot through. Hong Kong versus Ukraine. Raises the costs from a low-effort political gambit to a real military campaign.
This comment reminds of one on HN from Kharkiv on the eve of the invasion. If you assume something can’t happen or cannot be opposed, that’s indistinguishable from an invitation for an autocrat.