As noted above, the US did actually attempt that in 1812. With British assistance, Canadians managed to beat them back, and burn down the President's House for good measure (painted white afterwards to cover the soot stains). By the terms of the 1814 Treaty of Ghent that ended the war, the US returned to its 1812 borders. In the Treaty of 1818, Washington and Westminster agreed in principle on the 49th-parallel border between the US and British North America, as it still then was, and that's where the border remains.

Americans prefer to see the conflict as a draw, as the US was not forced to yield territory (though it did so voluntarily in the 1818 Treaty), and neither side was ever again game for a re-match.

Canadians, of course, celebrate the war as a Canadian/British victory, and a key event in building Canadian identity. (Stephen Harper was a big 1812 buff during the Obama Administration for some reason.)

Times have changed.

Annexing the True North (or at least the densely-populated southern part) would not have been an especially difficult assignment for the US armed forces, had President Trump cared enough to replace Justin Trudeau with Maxime Bernier or Danielle Smith---no more difficult than the 1938 annexation of Austria, say. Our southern neighbours outnumber us by about ten to one, and outgun us by a lot more than that.

Among the goals of our foreign policy towards the US (like that of the UK after the war of 1812) is to make sure the US is never again tempted to "liberate" Canada---much like Finnish foreign and economic policy towards the Soviet Union before 1991. Much of the time, that means doing what Uncle Sam wants us to do, regardless of how keen we might be on it. We're NATO members in good standing, for example, and don't seriously oppose US hegemony in the Americas, even when the US is in the hands of someone with little interest in liberal democratic values (a Nixon or a Trump).

If Tucker were serious about regime change in Canada, I'd ask, sure, but why? The threat alone is enough to convince the Canadian "regime" to go easy on anything that might annoy assholes, Canadian or American.

The Emergency Act was a very last resort, applied when local police (depending on who you ask) either were overwhelmed by the task of removing protesters (many camped on private property long after they'd worn out their welcome from the owners) who refused to move on, or, being disproportionately assholes themselves, simply refused to take action against their own.