Would you be enthusiastic about relocating if this was forty minutes away from Vegas in the desert?
US could build a new town 50 miles out of San Francisco with 4tph.
Holster-Gilroy looks potential. Petaluma-SantaRosa too, or Fairfield.
From a Quick Look on the map Those could all massively increase in size and be easily commutable to the entire SF area
Why would the current residents allow such a (presumably hostile) takeover?
If by people you mean 18th century farmers or 19th century merchants, sure. I guess you could make some semblance of an argument for countries like Belgium or Japan, but it's downright ridiculous to claim United States, one of the most sparsely populated developed nations, already has all the large cities it can support.
Increasing population merely to EU average would create housing for hundreds of millions.
That was not my argument, please don't twist my words.
I was replying to the idea that you should be able to take empty land and turn it into good cities. The reason that would not work is empty land nowadays is in pretty unattractive places. It worked 300 years ago I assume.
Sure you can turn a suburb or town into a city, that's how cities appear after all.
The areas where you could easily do something that provides work for a lot of people are already occupied by large cities, near river deltas, trade routes and coastal areas good for ports.
The only recent exception is SpaceX's Starbase town. And they could do this because of a very new 'requirement', frequently launch rockets where you have a south facing coastline as close as possible to the equator.