Ah I see. That's where the disconnect is. First when activists talk about housing density it's not just the commute they are talking about. They want the homes to be smaller because of the heating/aircon issues and no lawns (because of the fertilizer/maintenance issues).
As to the COVID problem, you still have an issue. It's not just the apartment rooms but also the shared plumbling, vents, sewage, elevators, common spaces, laundry rooms and garages of shared higher density living situations...the data on that early on out of China was quite clear, where because of the one child policy and the older people live out in rural villages you didn't have people crammed into the apartments (but apartments crammed into buildings). Further, you have a building issue as concrete and other building materials also contribute to global warming....you are now building more housing for the poor to break them up in different apartments instead of cramming them into one apartment which is the opposite direction you want to go.
The two problems you articulate (few homes per square mile, and two few homes per million people) are actually more linked than you want to think (probably because you don't want to see the implication). A review of Soviet housing (and their resulting horrible prescription) is illustrative. And if you think Americans are going to give up their single family homes for the Kruskayas, you're crazy....not going to happen in the absence of the Bolivaran revolution.