There's so much land we could quadruple the population and not even notice it. Have you not ever looked out the window of an airplane. Most of this country is unused forest.
I've seen the population double in my lifetime, and I noticed it plenty.
I'm talking prime real estate, pal.
You can live in some flat, boring, landlocked desert or flatland hell with the rest of your zillion immigrants if you like, just make sure your pollution doesn't drift over my property.
Seventy square miles of salt-water ocean front property for each person in a climate not too hot and not too cold is my ideal.
When you've run out of land for that, you're overpopulated.
And we've long since run out.
Even before Europeans arrived (driven out of Europe by overpopulation there), the Indians were overpopulated.
And it keeps getting worse.
Have you not ever looked out the window of an airplane.
Funny you should mention that.
Looking out the window during my first plane trip, down the East Coast, was a horrific lesson in how fast seemingly vast natural wilderness can be paved over and built upon.
It was houses all the way down, and it hasn't gotten any less crowded in the decades since.
Most of this country is unused forest.
May what's left of our unused forests ever remain so.