It’s not so bad if you are in fact walking most places and spending less time in a car. True it’s better than commuting somewhere far, but if you compare to living without a car in an urban core, it’s unlikely your footprint is smaller. Especially if you now live in a 3,500 square foot detached single story home that consumes a lot of heating energy, whereas in a city you’d have say 1,500 square feet with two shared walls and a shared ceiling/floor (basically you have a larger footprint based on insulation and exposed surface area).

The problem is most US towns and suburbs are not set up to be core walkable, dense places, where you don’t even need a car to get home. There are exceptions (I can think of some Hudson Valley towns on train stations, where their core has mixed use multi-story attached housing), but that’s not the norm and is generally discouraged via zoning.

Totally true. And as I think about this more, I'm not thinking enough about other impacts of that sprawl: Sure, I'm not driving as much, but that's because I'm getting a lot of things delivered to me, so SOMEONE is driving around a lot on my behalf (and I'm having to pay for it too).

Although with package deliveries, the impact is amortized by all the packages so the impact is probably less than if I had driven to the store, this isn't true of grocery and food deliveries. Those are about as inefficient as would be if I did that driving myself.

The approach of thinking about suburbs/city/etc will all have to account for the new hybrid lifestyle of remote work now – where people are living in remote areas but still not driving that much either.

Goods have to be shipped farther to reach you. You have to drive more than you might if you lived in a dense city (or dense town, but the US doesn't really have such a thing—hell we barely even have dense cities, really) even without the commute. You require far more installed and maintained pavement to maintain your quality of life. Utility runs are longer, so, more ongoing maintenance costs, which means more fuel use and more use of materials (so, also more fuel, ultimately). And so on.

Less-dense housing strongly tends to be less-green than denser housing, commute or no commute. The differences are extreme enough that yeah, it's pretty close to being that cut and dry.