My son went to a new farther school this year, it took nearly a year for my wife to get used to the fact that he goes there alone (bike / public transport). However I had to buy him a phone to know his location in order to ease my wife.
I'm not naturally worried, but i got contaminated by her stress.
I don't know where the stress comes from. I think it maybe maybe the lack of trusting other people: you do not trust that strangers help you
Well I'm in Europe (Romania) too and street crime is basically nonexistent where I live, yet I don't let my 11 years old kid commute home by himself. Problem is cars, he only has to make a mistake once and I can't afford that mistake.
I grew up in the countryside in the 80s, cars there were as rare as hen teeth at the time so entirely different situation. Also parents used to have 2-3 kids back then, I only have one so gotta pay extra care coze there's no backup :)
I suspect that part of the worry aculture around parents being overprotective of kids today (at least in the west and the U.S. in particular) comes from exactly what you mention, a prevalece of single-child homes with no backup so to speak, vs increased worry in general.
As European, it varies a bit per country, naturally not always without possible issues, and as a 1970's child back then the freedom was much bigger, still in general we still have the general attitude of not calling authorities just because kids are having fun on their own.
All the best, and maybe something for the 1980's US kids that I just watch recently from a stand up, that touches how US lost this culture.
"Why 70s & 80s Kids Rule: The Ultimate Guide" by Karen Morgan
I don't get that call the police culture.