In the mid 20th century we felt comfortable leaping into cars because everyone assumed prosperity would increase infinitely forever. But one of the biggest downsides of car infrastructure is that it's extremely difficult to downgrade to a different system if prosperity ever decreases. A streetcar infrastructure for instance can safely downgrade to bicycles and walking if for some reason the streetcars can't be run anymore (which itself is unlikely), those methods will be more annoying but they'll still work. But a subdivision and strip mall infrastructure is so spread out that it can only be traversed by car, so if the cars ever become too expensive to own and operate (which can happen easily), the society simply ceases to function.

It's a system that fundamentally lacks resilience compared to walkable infrastructure based around trains for long-range travel. When prosperity decreases America can't just safely become poorer, it has to suddenly and violently fall apart.