Have you actually ever driven across the United States? Very little of our country is populated to any great extent.
You are correct. There are vast, wide open spaces in our country with no one living there. Problem is, you get enough bored billionaires like Bill Gates or Ted Turner, who keep gobbling up what is there, that reduces the open space.
Oh, and BLM (Bureau of Land Management) who control at least 12% of all open space in this country.