In the US, if you are in a residential neighborhood with a lot of kids, its also fairly typical for them to be out finding their playmates.

I would say if you're in a neighborhood where there's just like 1-2 kids, it may not be that typical. The kids parents might do more scheduled playdates.

Unfortunately in the US there are people that get annoyed about kids playing. And they are also the same kind of person that escalates things to the authorities / complains a lot about trivial things.

There's a Netflix documentary about one such sad case https://www.netflix.com/title/82018736

This. Those of my friends with kids moved to neighborhoods and suburbs where other households of a similar age existed.

You see this in SF, with singles primarily living in the Marina, Russian Hill, or Rincon Hill and then upgrading to Mission Bay once they have kids.