None of that laundry list ultimately matters when Japanese speed limits are so much lower; speed is what kills. (Also, Japanese drivers are used to keeping their cars in lane, are used to sharing the road, and are driving much smaller and lighter vehicles). I suspect that what you perceive as "absurdly fast" is probably very different between those countries: because of the absurdly wide roads in the US, absurdly dangerous speeds get normalised. Someone doing 25% over the speed limit in Japan is still driving much slower than a driver in a comparable neighbourhood in the US.

> Some particularly busy intersections require dedicated police officer supervision to shepherd the drivers because they're so unruly and disrespectful of pedestrians and other drivers.

So like any intersection in New York.

> There are many reasons Japan is more accepting of letting children be children, but most of that is social factors and motivators that are decidedly different from American ones. Cars are ultimately just a really small part, if any.

Nah. It's cars, more specifically street parking.