Very little land...in all... of North America. That's a big place for such a tight summary lol.
The communities,, space, and zoning are out there, but often many facing the housing issues just aren't willing to move. There's more to it than this obviously, but for every person slamming their lifestyle and expenses against the wall in a trendy area, there are others picking up and moving to Philly, St. Louis, Lexington, etc.