I grew up in a European city and never once took a car to school. I walked to primary school, junior high and high school. Then I took public transport to university.
I know most cities and neighborhoods aren't set up for that in the US, but if it can be done in Europe it can be done elsewhere.
Walking to primary school at 5yrs old is not going to happen. I don't know which primary school you were in but sending your kid alone to school at that age seems improbable.
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.
I know most cities and neighborhoods aren't set up for that in the US, but if it can be done in Europe it can be done elsewhere.