"Walking" doesn't imply "alone". When I was too young to walk alone to school, I walked to school with my parent.

Why not? Excepting the differently abled, most 5yos are perfectly capable to walk to a bus stop or less than a mile, I sure was. The streets are safer than ever in history despite the fear-mongering you see.

If america has a problem, it is 'protecting' its youth from the 'big bad world' rather than helping them to explore it.

There are homeless people on the streets injecting drugs into them. And to send your 5yr old into that path will likely result in challenges.

And stop with your America has this problem and Europe doesn't. Each country has its pros and cons. And people make choices accordingly.