Average over what, though? I'd assume that 1sq in a dense metropolitan quarter in high demand goes for a lot more than 1sq in a poor neighborhood or in the middle of nowhere.
The global average doesn't really mean anything except "somewhere in the US there is still affordable housing".
Most critics of rising housing prices that I know of aren't arguing that housing is becoming unaffordable everywhere but that it's becoming unaffordable in high-density places where housing would be needed.
You acknowledge this in:
> This pushes the price per square foot inside metros up way above what they would otherwise be.
Also shouldn't actions include at least having a look at building speculation in high-density areas?