And a very basic part of it is simply geometry: the more people you have in a limited area, the harder it is to build homes for all of them. Historically, there simply were FAR fewer people, and so finding place for homes was never a huge issue. The cost of housing is mostly property, not construction costs.
The US is huge with a low population density, why not just expand the cities a bit or build a few new ones? Is there some reason why this can't be done?
> Throughout his campaign, Trump focused on deregulation, tax cuts and reducing mortgage rates. In speeches, including one at the Economic Club of New York in September and a press conference in August, Trump reiterated his promise to reduce regulatory barriers and vowed to make federal land available for extensive housing projects.
https://www.housingwire.com/articles/trump-housing-build-fed...