> The solution is pretty simple: build and unreasonable amount of housing. And entirely new cities.

So it is not simple. "Just build more" always comes up in those discussions, and while it does help (and has been proven to help), it is not the definite answer for the housing issues.

Build a new city from the ground up with a bunch of cheap modern housing, walkable and all modern goodies and ... nobody will move. People don't move just because housing is cheap. Actually many people are willing to spend a significant amount of their income to live in specific places. We move to have a job, to build a career, to be close to friends and family, to have better access to entertainment and activities, ...

This is why most developed country experience rural flight. The housing crisis is (mostly) a big city problem. You can usually find extremely cheap housing if you go deep in the countryside. And building is also cheaper (the price of the land is less, there is less permits issues, etc).

And for big cities, "build more" is way more challenging. Ground space is limited, so one solution is to build more vertical, but it is costly and has its own limitation. Spreading may cause issue with water management and require big investment in a public transport infrastructure if you don't want to have a nightmare traffic. Pollution can be a very big issue, etc. And that's for all the non-political issues. The political side of things can get very messy, very quickly.

If there was a simple solution, every big city in the world would have done it by now.

America already has plenty of cities that aren't doing very well, and aren't getting migration, so new cities aren't going to help. There's plenty of cheap housing inventory in the US, just not in the places where the jobs are.

America doesn't need new cities. There is an unbelievable amount of space wasted within every city and any urban planner can show you. Development policy in the 40s and 50s was backward and we continue to suffer the consequences today.

World is full of empty houses. It's just that people want to live in New York and not in some other place where housing is cheap or, occasionally, even free. And New York is already pretty full.

Detroit had tons of extra housing. Why have people people fled to other cities?

There is no easy fast solution to this. Just build more housing will not solve complex issues. Not saying there should not be more construction, though.

I'm not sure how you get there without killing or violently subjugating tens of millions of people.

Everything preventing what you want is backed by a law. On the other side of that law is someone making a buck either via business being driven straight to them or business being driven away from someone else and they will fight to preserve it.

Even a simple amendment to the clean water act to exempt residential square footage would have every asshole who makes money off an engineering stamp up in arms. Even some guy who designs bridges would be pissed because he doesn't to compete with all the other labor that would put on the market.

Wash rinse repeat for literally every other issue that's roadblocking the construction of housing.

And this is assuming you want to just develop existing areas further (turn suburbs into cities, exurbs into suburbs, as happened from ~1870 through ~1970). Creating cities from scratch is way harder. Where are those people gonna work?

See Detroit mid-2010s for why massive overbuilding isn't a good strategy here.