Conversely, I have traveled to Europe and Japan. At least in the areas I went to, it didn't really seem any safer for kids to play outside than many parts of America. Yes, public transit was much better, but there were still lots of cars on the streets, and there were areas that weren't very pedestrian friendly. And in some cities it was quite difficult to find playgrounds. I don't doubt that there are places in Europe and Japan where kids can play outside without worrying about cars. But such conditions are not universal.