The Canadian's had their own counter plan: https://en.wikipedia.org/wiki/Defence_Scheme_No._1 It would have been a gigantic failure. The plan was to try and mobilize quickly, seize Buffalo, Detroit and Seattle, and hold on for dear life until the BEF arrived. But the British were clear from the beginning that they were never going to send significant reinforcements to Canada: the ocean was too large, the USN too strong, and the Canadian plains too vast for the British army to be able to effectively defend. At most they might try and send some troops to defend Halifax as a key naval base. So the Canadian plan ensured that their best troops would be lost quickly, that the Americans would be super-pissed off and unified, all for an ending that would never come. So while it might have made sense militarily, it could never have worked politically.
The US war plan for the UK was similarly weird: according to Miller, _War Plan Orange_ War Plan Red was the result of a deal between the US Navy and Army. The Navy wanted War Plan Orange (war with Japan) and so they let the Army write War Plan Red (the UK). Which was why a war between the two mightiest naval powers on the planet in 1925 called for the US Navy to be on the defensive, at most seize the Bahamas, Jamaica, and Halifax to try and deny them as bases to the RN, and then the US Army would invade a separate nation (Crimson aka Canada) that would probably try and be neutral in the war!
Basically, from what I can tell, the US, Canada, and UK were putting their best war planners on the likely threats, and putting their less experienced and good planners on these war plans. Because War Plan Orange was, at least if you squint, how the US defeated Japan. And the Canadian and UK's war planners for mobilizing in World War Two and sending them to France did a bang-up job. It was just these plans that were not thought through and would have been disasters if implemented.
Any war between the U.S. and Canada would play out in strange, unpredictable ways just due to how closely intertwined pretty much every critical capacity of our two nations are.
Both the West and East coasts would immediately have their power grids upended by the loss of Canadian hydro. Fuel supplies (and practically everything else in both countries) would be disrupted as Canadian suppliers turn off the taps and American refineries go dark. Pipelines would, in all likelihood, be sabotaged so that they can't be started up quickly even once controlled. Large parts of Canada would go on a sudden bread and meat diet, since they rely almost entirely on imported fruit and vegetables.
Neither side would likely have the element of surprise, since both sides would be compromised by a large number of people in their command structures who are either from the other nation or sympathetic to it. A significant portion of U.S. forces would likely refuse to follow orders unless there was a damned good reason to invade Canada. Civil unrest in the U.S. itself would be a huge problem for the same reason. U.S. rivals such as China would pounce on the opportunity to take advantage of things while all this is going on. If the U.S. rolls into Canada then nobody is going to give a fig about Taiwan.
Occupation would be another matter entirely. The territory is massive and the enemy indistinguishable from yourself. Canada would present many of the same difficulties with terrain as Afghanistan, but with a populace that can tell which end of a toaster to plug in.
Since when does the US west coast depend on Canadian hydro electric generation? WA state has so much hydro the price goes negative every spring when the snow melts. There’s a half dozen LNG generators state wide for supply stabilization, several wind farms and solar arrays.
And the line loss would be too great to economically ship canadian electricity to California
Being able to import a few percent when you need it and export a few when you don't without having to spin something down is pretty important to having a stable power grid.
The reality is that there is no dividing line between Canada and U.S. when it comes to electricity. Power grids cross the 49th at will. In California, you're on the same interconnection as Vancouver and Calgary.
Conflict would disrupt power in both countries, and much further from the border than you may suspect.
I mean, this is all true for a war today. But the economies were not intertwined as tightly in 1925, which is when these war plans were being drawn up. The US and Canada had had a pretty nasty border dispute (at least from the losing Canadian side) just twenty years earlier, well within the memory of most politicians running Canada. (I suspect that most Americans had forgotten about the Hays-Herbert Treaty of 1903 by 1925, but it would have been far more prominent in Canadian minds.) With the passage of another century I would be honestly shocked if such plans existed today on either side.
The US war plan for the UK was similarly weird: according to Miller, _War Plan Orange_ War Plan Red was the result of a deal between the US Navy and Army. The Navy wanted War Plan Orange (war with Japan) and so they let the Army write War Plan Red (the UK). Which was why a war between the two mightiest naval powers on the planet in 1925 called for the US Navy to be on the defensive, at most seize the Bahamas, Jamaica, and Halifax to try and deny them as bases to the RN, and then the US Army would invade a separate nation (Crimson aka Canada) that would probably try and be neutral in the war!
Basically, from what I can tell, the US, Canada, and UK were putting their best war planners on the likely threats, and putting their less experienced and good planners on these war plans. Because War Plan Orange was, at least if you squint, how the US defeated Japan. And the Canadian and UK's war planners for mobilizing in World War Two and sending them to France did a bang-up job. It was just these plans that were not thought through and would have been disasters if implemented.