Realistically, as long as the US is a stable ally (which is currently in dispute), what does Canada need from its military? It's highly unlikely to be attacked based on distance to potential foes and proximity to the US. An attack from the US would be hard to defend on a military basis --- the difference in forces is overwhelming. Canada would need to heavily rely on alliances to defend against attack from the US, but logistics would be difficult; better to push on diplomacy and/or convincing US armed forces to refuse orders to attack their neighbor.

The Canadian armed forces participate in international missions in cooperation with other forces, and in domestic matters. You don't really need fighter aircraft for domestic missions; and for international missions you need whatever will work in coalitions. With a stable US pushing the F-35, the F-35 is a reasonable candidate for coalition work. Without a stable US, the F-35 is a poor candidate; presuming Canada would continue to be allied with NATO ex-US, whatever that group decides is the future is going to be a better choice.