The area in the red is one continuous granite slab called the Canadian Shield. The US has no comparable geography.

There's almost zero topsoil, and building any community there involves a lot of very expensive blasting. It's bad land for the opposite reason that the Australian continent is largely uninhabitable: there's tons of water, but no soil.

(The only real upside to it is that it's very conducive to hydroelectric energy; the vast majority of Canadian energy production can be, and has always been, zero-emissions- we call electric companies "the hydro", and combined with the nuclear reactors in Ontario, 85% of national electrical power generation is zero-emissions.)

Superimpose a population density map on the Eastern provinces, and you'll notice that generally speaking, the settled area of the provinces ends where the shield begins. That isn't a coincidence.

Sure, climate change should make a bit of the [non-red-shaded] land more economically useful, but that's about it, and mining/farming communities generally aren't large enough to provide a base for a new city especially because it's landlocked- so you're not going to see any new cities spring up there any time soon.

I think you're just ascribing cause when in fact northern Alberta is just as empty but has no Canadian Shield.

I was going to say, there is still a lot of land both outside and inside the “Shield”.