Can you include the barely inhabited Rockies, the Badlands, the arid low and high deserts, the Sierras?

First of all there are population centers there but I guess if you look at a night picture they aren't large at this time: https://www.census.gov/library/visualizations/2000/geo/popul...

(Keep in mind that picture was taken when the US has 58 million less people or 17% smaller than today)

But we also have to understand that the US continent could grow to a billion people and still only have the density of France. That is not a matter of lack of land, its a matter of political will.

There have been attempts to push this idea: https://ui.charlotte.edu/story/why-not-1-billion-americans-o...

Anyway given that the land is sparsely populated it is still a fair comparison: When you have such a small population but access to such abundant resources that few others have on the planet, you are going to end up in a scenario like what the US has now.