The relevant metric is land within a reasonable commute to an attractive city centre.

This is not in short supply either. In California, the capital of the American housing crisis, the overwhelming majority of new residential development in the last 50+ years is low-density single-family on greenfield land. This is certainly true within the high-demand metro areas like the Bay and Greater LA. We could multiply the housing supply of these metro areas by many times without ever building on greenfield land ever again. The land is unbelievably not scarce. It is just illegal to put a sane number of people on it.