Have you actually experienced Japanese drivers? They make American drivers look absolutely noble (and truthfully, we are) by comparison.
For starters, and this applies to both individual and professional drivers:
* They don't give way to emergency vehicles blaring the sirens.
* They don't wait for people to finish crossing intersections.
* They don't let other drivers into their lane.
* They drive absurdly fast.
* Most roads are very narrow.
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.
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.