[s1artibartfast]

That doesn't really explain the changes over time in US behavior and child Independence. The US had a very strong car culture in the '50s to '80s as well, but children would still roam the streets on bicycle and on foot

[zhdc1]

It’s one thing to accomodate cars, it’s another for the entire landscape to optimize against them.

The average suburban family in the 1980s had a car. They also had well maintained sidewalks, civic organisations, and - in many cases - stores within walking or biking distance.