The housing shortage is so much worse than you think, because the bar should be 2 or 3 homes per household. The upper middle class gets this, why not everyone? I think every family should have a city apartment, a country house, and a vacation home. That's a shortage of like 250M homes! Materials? Houses are easy and cheap; that's not where the cost is. Emissions? It's never been easier to build low-carbon: solar, desal, heat pumps, batteries. Density? US would still be less dense than EU. Land use? Build up in existing cities and you'd hardly notice.