My point stands.
Eh.
Canada is cold and isolated.
The truth of the matter can be found on something like this.
Population distributionI know uninhabitable means you can't live in it, but it is quite obvious that Canada is not a superb place to live in. Albeit, it contains many natural resources, they are in cold places.
The biggest thing that effects Canada's climate is it's population, and climate typically has a much smaller range in coastal areas. [Looking at that map, you can see that people like the coast!]
Now, of course, coasts offer many more opportunities besides a good climate [harbors and fishing and shipbuilding and oil and stuff]
Yet, it is clear that a lack of ocean-created humidity leads to a serious depletion of airborne heat during the winter.
A good counter-example to your argument is the state of Montana. It, too, could hold a good 5 Million people, yet, currently has close to 1. If you were to look at a population density map of the US, you'll see the middle is less populated. Canada, unlike the US, is also much higher up, obviously giving it a lower average temperature, but, what's more, a shorter agricultural growing season. Personally, I would see it fit that a country that cannot grow so much food would have a low population, as own-grown food is always a nicer thought.
Overall, it makes perfect sense for Canada to be so unpopulated. It is cold and harsh, and although it has great places. [Coastal BC, has a warmer winter than most of the USA!], the majority of that land mass is a bunch of chilly forest -- not because it can't compare with the American birth/immigration rate, it is because nobody wants to be born/emigrate to some of those places.
I'm sure, if people tried in Yukon, they'd have some millions there -- but why not just party it up in the Northeastern section of the US -- with more jobs, heat, an actual growing season, etc?
So the point isn't really there, Canada will never boast a population of a modern country. Even a place like Stockholm, Sweden won't work. Although it boasts 2.1 million people in its metropolitan area, that area is also home to 22% of it's population -- and, obviously enough, it lies on the coast, and is a rather warm city for that kind of northernness.
Russia, also proves the same point. Siberia, having around 70% of the land area, has 4 ppl per square km, whilst all of Russia together has around 8, indicating that the coastal section is pulling a lot of weight to keep that number at 8.
*****
Overall, I think that if given an option, people will pick the warmest places. Shade, water, AC, houses, helps to kill heat, which can go away in the night. Cold, though, is, I think, a lot worse, and annoying.