There is zero chance that a land dispute between the US and Canada will ever have anything to do with which fighter jets either side has available.
The issue comes down to whether the passage is qualified as territorial waters or just exclusive economic zones and how the islands are connected to the mainland may determine that. Regardless, the US is pushing it because it's a useful way to get concessions on other issues. Like him or hate him, understanding and using that aspect of negotiation is one thing Trump was always very good at and in this case Mike Pompeo was the one putting it forward and lobbying other countries to see it their way.
Purchasing the F35s has been discussed here since at least 2007 when Russia was flying bombers into Canadian northern territories. Something is needed to respond assert sovereignty over the area. A potential issue in theory of purchasing the F35s is a strategic one of maintaining those water rights if in the moment Russia starts moving in suddenly the planes don't work or need parts and the US suddenly has a great point leverage.
There is militarily 0 need to use an F-35 to intercept Russian bombers. Actually the F-35 is pretty bad at interceptions. The F-35 has a pitiful 1100km combat radius, and cannot supercruise. The Gripen is a bit better and may be able to supercruise meaning that it's effective interception range is significantly better, and most importantly can usefully utilise drop-tanks. Even the CF-18 is a better interceptor than the F-35.
The F-35 is not the right choice to deter Russia in the arctic. It's the right choice if you're planning an invasion or need to do strike missions past enemy air defences, or if you're going to be doing air-to-air combat far from home.
