Earlier quoted context omitted.
Driving isn't negotiable, when living in the USA outside of the few major metros. Unless you've done it, you may not know what I mean. Most of the US is truly remote, even from the closest grocery store. Health doesn't play into the practical consideration of the way most of the country needs to traverse needed distances.
I've visited the U.S. a couple of times on holiday and even from that perspective, it's stunning just how many places are designed exclusively around the car. Even just walking from one shop to the next is awkward as they often have fences or hedges to separate them, so you have to walk from the shop, through the extensive car park, onto the main road that has no sidewalk and then into the next car park. But yes, you…
The US is wildly low-density outside of the major metros. It's one of the better things about this Nation.
Conversely, the very dense portions are built for cars and facilities are relatively close but still require a car to reach on the whole.
I live an a very dense major urban area, just outside of the city limits, and there isn't a single walkable store that isn't a convenience store with a gas station, a drug store, a rare butcher, a bar, a liquor store, a beer distributor, a tobacco store, a laundromat, and a pizza shop that serves bad food. And most of those aren't a short walk, though I need none of them aside from the butcher.
The grocery store and anything else absolutely requires a car. The trend isn't toward more such facilities, but less. Social (crime) and economic pressures are causing the food desert to expand. I know people who live 3/4 further away from me, across dense urbanity (which is a lot to travel, especially for older people), who need to travel to the suburban food store that I go to. There isn't space between it and them to build another grocery store. Less adaptable and more vulnerable stores have closed.
I agree that there is a limit to dense usability given any metric, but the dense areas are already designed. There isn't an option to redesign them as they represent vast expanses of residential homes. I don't see exurban areas filling in any time soon, especially given fuel / electric costs and economic pressures in addition to higher interest rates that will slow residential construction for the forseeable future. Also, they are truly vast.