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.
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 :)