This is a bit of overblown "look at the crazy foreigners!" Most people don't raise kids through the same ages in multiple countries so they have no idea what the real differences are. There is also more variation in the USA.

Here in San Francisco you can go watch little kids doing this exact same thing every single day. Teachers walking the kids to Golden Gate Park, showing them how to wait for the WALK sign, look both ways for cars, etc with no parents around.

It is also extremely common advice to make your kids cleanup after themselves to learn responsibility. At 18 months they naturally want to help, so you give them jobs to do and slowly ramp up the complexity.

The only thing unique to Japan (that I got from the article anyway) is that really young kids walk to school by themselves. Part of this might be urban vs suburban/rural, I'm not sure. SF doesn't bus kids, and I definitely see middle-schoolers navigating muni on their own. Not sure how much younger that goes.