Fighting a war against the US is futile. Not saying it should be annexed but if it has to be anyone then it may as well be your neighbors who have a lot in common with you. Life in Canada would no doubt improve if it was a US territory.

I think that's a bit shortsighted. It's sort of an open secret that the current US admin is doing russia's bidding. Obviously America will lose a lot more than gain if it attacked or invaded Canada. There is nothing canada has right now that is inaccessible to the US, the US can deploy troops, bases, train soldiers,etc.. if it had peaceful relations with Canada. keystone XL is sifting canadian oil to US refineries, alaska benefits a ton from canada based supply chain and airspace, alaska strategically is extremely critical to the US, far more than any part of canada, because it's proximity to asia, the US itself and europe by way of the arctic, it is a major (if not the most important) logistics hub the US has in the western hemisphere (I'd say Ramstein in germany is the only other more important hub the US has). All to say that canada attacking alaska would be devastating to the US. If canada simply stopped all relations with the US, I'm pretty sure it will cause a major recession in the US, if not a depression outright. Again, all THAT to say that the hostility against canada is not being done on behalf of the american people but on behalf or russia. Similar to how the hostility against EU via greenland is meant to destroy nato for the benefit of russia.

Russia cares a lot about controlling canada and greenland because of their desire to dominate the arctic. They already control one half of it more or less, but as I mentioned earlier, the fastest way to europe from the americas, and even from eastern russia and north eastern asia to western europe is via the arctic. They want ukraine to dominate agriculture, and gain warm water ports, the arctic to control shipping lines and flight paths (including ICBM flight paths :) ).

With a presumed fallen global order where Canada and the US are not allies in the least, Russia has every reason to invade Canada, if they decide to control all of canada, that'd be an immense victory for them, outside of china no one can stop them from global domination at that point.

Strategically, what Ukraine is for europe, Canada is to north america.

Russia's arctic fleet supposedly is even superior to the US navy's from what little I've heard about the topic. Wars aren't that simple either, Russia hasn't mobilized or entered full wartime mode yet with Ukraine, it's still a "special operation". They're more than willing to mow down tens of millions more of their people. Another interesting aspect of a prolonged war is that they start building internal supply chains to build tanks, artillery, basic supplies,etc.. that is if their economy doesn't collapse, which it hasn't. Oil sales is still keeping them alive (in no small parts thanks to europe). But I'm sure putin is content merely controlling canada via the US as its vassal state.

Gripens with external tanks outrange F35 with external tanks flying dirty, and since 4th gen, stealth hardly matters. Spaced based ISR is proliferating, in 10 years F35s will be picked up through SAR from space if not already... well depending on adversary. PRC and US, stealth broadly not meaningful. IMO RU hardly relevant.

And to be blunt, RU/PRC is MORE aligned with Canadian position on Northwest Passage sovereignty. Which really only leaves US... i.e. the only actual on paper threat to NWP is US, which makes F35s terminally stupid acquisition for CAN arctic. But broad IMO is Canada simply doesn't need a strong air game because it won't survive vs adversaries operating in the north anyway. Geopolitically, Canada needs F35 to NORDAD dues/ransom more than it needs F35 for tactical/operational needs. Cue CAN buys f35, find them ruinously expensive to operate, and US will end simply "patrolling" Canadian airspace anyways.

Wait, does the US sell any stealth planes? I thought that was special secret stuff only for US usage.