I doubt that... there's actually ample land for everyone, we've got entire cities, hell, provinces or states, that are virtually empty. North Dakota for example has 10% of the people of Massachusetts, but 7x the land. That's a roughly 70x difference, we're talking about having say 1000 square feet vs 70.000 square feet of space. There are obvious reasons why one state is more easily suited for living (weather, distance from ports or rivers are lacking in ND), but in the 21st century it's certainly also easily possible to house an order of magnitude more people in ND.

And it isn't even just a discussion about low density states vs high density states. Take one of the highest density states, Massachusetts. Its density is about 800 people per square mile. That's nothing... A square mile is almost 28 million square foot. You're talking about having about 35 thousand square foot, per person, of space.

In fact, here are some images of population density of 100.000 people per square mile, more than 100x more dense than one of the highest density US state averages:

https://ggwash.org/view/42469/what-do-80000-people-in-a-squa...

And here's an interesting article about the amount of space needed to give all 7 billion people on the planet a standard vancouver house+yard lot.

https://vreaa.wordpress.com/2011/12/09/land-not-making-any-m...

Which also cites another calculation on how the entire world population could fit into Texas if it were built as dense as NYC.

The issue isn't really sheer population, it's population distribution. Proximity to other people means proximity to jobs, culture, networks etc. And that means we see small plots of land become extremely scarce and in high-demand, and large plots of land become extremely abundant and in low-demand. You can see this if you look up economic heatmaps of the US, it's pretty insane. Most countries are basically a collection of a few cities where all the money is made and everyone lives. I wouldn't be surprised if cities became the dominant political unit rather than nation states. (not legally, but in practice). I can't find a great image at the moment but this gives an idea: https://cdn.howmuch.net/content/images/1600/where-the-money-...