I was thinking about that when I was dropping my 6 year old off at some hobbies earlier - it's pretty much expected to have learned how to ride a bicycle before starting school, and it massively expands the area you can go to by yourself. When she went to school by bicycle she can easily make a detour via a shop to spend some pocket money before coming home, while by foot that'd be rather time consuming.
Quite a lot of friends from outside of Europe either can't ride a bicycle, or were learning it as adult after moving here, though.
edit: the high number of replies mentioning "swimming" made me realize that I had that filed as a basic skill pretty much everybody has - probably due to swimming lessons being a mandatory part of school education here.
That leads to a follow up question to people from different areas: Is swimming a regular part of school sports?
I grew up in Germany with pretty much no lakes, and we had blocks of sports classes in the swimming pool from first grade - didn't make me a great swimmer, but I can go swim a bit in a lake without having to worry.
Now we're in Finland (lots of lakes here), and also swimming classes take place from first grade.
American here. The nearest swimming pool to my hometown was in Canada. So no.
Edit: I don't think this is normal
Also american here and I learned to swim before I started preschool. But I also live in the land of 10,000 lakes so it's basically a requirement here. So this is another one of those things that is going to depend on which state you're in.
Oh yeah, I make no claim that any of my experiences are anywhere near universal. Basically no part of the American experience is.