By geometry problem, what I mean is that an individual car just takes up far too much space (both while moving and while parked) to be compatible with even a moderately dense environment. You need some kind of rationing or metering.

The presence of cars alters the built world in a direction which favors more cars. There are more parking lots, which means less density, which means fewer people can choose to live closer to work, which means more cars, and so on. (Transit does the same in its own favor, of course. Transportation is quite fundamental.)

It is true that transit doesn't work as well with how post-war American suburbs are typically laid out. But it works quite well with the levels of density in pre-war "streetcar suburbs", like those built around the Key System in Oakland. I think the most reasonable solution for post-war suburbs is transit most of the way, and cars (robotic or otherwise) for the last mile.