Yes, I'm guessing that many of those urban areas are within half an hour of a freeway--though this may be less true in the West. But the vast majority of those 82% don't live in places that are remotely walkable.
According to my Google search, Japan's urban population is 90%+. The US is around 80%. That's why I mentioned the two places.
/s obviously.
God I hate the responses on threads like this that insist on the impracticality of public transport worldwide because it doesn't work in the US. It's like mass Stockholm Syndrome or something!
Notice how I even said "it works in places like Japan"? Notice that? See it? Good. Now quit acting like like you're being oppressed every time someone mentions the US. Yes, the world is a big place, but guess what? The US exists and a lot of people live there. Deal with it.
Jesus christ it's like I insulted your mother or something.
What matters is if the 82% of Americans who live in cities are forced to crawl through sprawling car-choked landscapes, or are able to live in a walkable environment. High reliance on cars prevents the latter.
By the way you were wrong about that Japan vs US comparison as well. USA has a higher proportion of urban residents than does Japan. And they have plenty of trains in Japan.