There was an article about a parent who tried to do exactly that, in America. But the parent did not throw the kid into the deep end. For at least a year, the child was taken on those errands, being familiarized with the rule of the road, introduced to store clerks.
Ideas this author generated include — sending an older child along; secretly following to observe without intervening on anything less than catastrophic risks; sending the kid to neighbors to borrow a cup of sugar (and acquaint them to the neighborhood), and so forth.
https://www.youtube.com/watch?v=9eMZp8KsZ5k
Is Japan safer than the US on average? Yes. Is the US so unsafe that sending a 7-year old to the neighbouring kids' homes should be frown upon?