Hypermobility in the service of jobs has broken a lot of that cohesion. You usually don't live next door to your parents, grandparents, uncles and aunts any more. This gets worse the more urban the area is - rural areas still have some of that cohesion.
Neighborhood socialization? Not in any apartment complex I've ever seen. Walk down the floor, eyes straight, avoid even basic salutations. It's slightly better in suburbia, but not much.
In the grocery store? Have you been to a large grocery store? It's not socialization just because there's a lot of people. What meaningful interactions are there in a grocery store?
This leaves church. And as it turns out, that's not everybody's cup of tea.
American's may not spend all their time in the car. They do spend exorbitant amounts of time in their care. They do have much less opportunity to socially engage than most Europeans experience. What social experience there is often needs large quantities of alcohol - and while I haven't seen any studies on the subject, I'm still holding the belief that at least a good chunk of that is due to needing to deal with the anxiety of an extremely uncommon situation.
As I said above, many of these factors are somewhat lesser in more rural communities, but they experience a large flight of the younger demographic towards cities, curtailing cross-generational interaction.
And that's not just an "uninformed view". I've spent several decades inside and outside the US, and seen a few cultures in the process - and that view holds. But let's dismiss that as anecdote, too, and look at actual data, time spent visiting friends per day[1]. The US is way down that list.
It's very likely car culture is far from the only reason for that, but the US is a country that seems fairly isolating.
https://www.statista.com/statistics/522039/time-spent-visiti...