The description of "Swiss parenting" would also accurately describe most American parenting 60 years ago.
From what I can tell, the mentality of not allowing kids to get around on their own has really been in the past ~20 years or so. And (IMO) it is largely caused by some subset of people who freak out when they see kids alone unsupervised. Other parents (like me) would love to give our kids more freedom, but feel limited by the possibility that nosy neighbors will call child protective services if we allow too much.
You have to gauge the area/neighborhood and find out what's common - do you see ten year olds walking around? Twelve? Fifteen? And then you have to get to know the neighbors to reduce the risks, and then deal with all the other issues that may pop up.
My kids don't walk to school (I get to sit in the maligned drop-off lane) because our school is unfortunately at the intersection of two very busy roads. I still think my kids could manage it, but literally not a single other kid walks to school so it feels like having my kids do so might draw too much unwanted attention. The school doesn't even have a bike rack, which is appalling to me. My memories of elementary and middle school were of many bike racks stuffed full each day.
My friends and I did ride our bikes all over town though. To the swimming pool, to the basketball courts, to our friends houses on the other side of town, and everywhere in between. I had to leave my mother a note when I left, and be home when the street lights came one. Other than that, we were basically on our own riding around town and drinking water out of random garden hoses when we got thirsty.
Disclaimer: I am not in the USA nor have experience living there.
Sadly, this is not always the case in the US. There's plenty of stories out there of CPS taking kids away from parents for extremely questionable reasons. A lot of time there are vague laws that they can use to back up their actions. For example:
> In Illinois, the law defines a neglected minor, in part, as “any minor under the age of 14 years whose parent or other person responsible for the minor’s welfare leaves the minor without supervision for an unreasonable period of time without regard for the mental or physical health, safety or welfare of that minor.”
"Unreasonable" is poorly defined, and overzealous CPS officials can easily claim that letting a child ride around alone in a neighborhood represents a "health and safety risk".
Unfortunately, these kinds of things have happened with CPS. I can't say how common it is, but the threat does exist.
I was routinely left to my own devices even as young as 8, me and my friends would be out roaming through empty lots and along beaches and stuff for hours in the late 90s
Stuff really seemed to accelerate past that. Partly because the empty lots filled in, the park with a rope swing got replaced with a playground with seating for parents...
Density does limit kids options too
I think the amount of independance I got would probably have been described as neglect if I had turned out poorly, and in my teenage years I really did flirt with a pretty bad path, but it turned out good so I remember it rather fondly.
By the time I was 11 I was biking everywhere with big groups of kids. Or my buddy and I would go to the store and grab a drink or snack.