I don't get what this comment is about. Is suburban North America especially dangerous for cats?

I suspect that they are meaning that suburban Americans are known for being very opinionated, judgemental, and overly concerned with what others do with their lives.

However, for your question, if on the peripheries, yes. There is danger to cats from cars but also coyotes, raccoons, and native big cats (bobcats, lynx, and cougars, as well as humans (was terrified for my cat when I lived in a place where serial cat mutilations started taking place). I grew up with outdoor cats but generally have preferred to keep them inside, unless it was not possible (people who think that it's a case of ignoring a "whiny" cat have obviously never experienced the craftiness and terrorism employed by a feline that grew up semi-feral in the woods).

My reasoning is very similar to you Finns. I distinctly remember, as a child, finding one of my semi-feral cat friends frozen to death next to a pond in the forest during a particularly cold winter. As a child, we also lost near a dozen cats over the years to wildlife and cat haters in cars intentionally hitting them. That's just too much.

I want my cats to live as long and happy a life as possible so, as an adult, when we adopted kittens, we kept them inside. They have windows, toys, and companionship that keeps them from feeling the need to be outdoors.