Public transit in the US just mostly sucks. It tends to be sparse, slow, unreliable, and yeah sometimes there are crazies who make the environment feel dangerous.

You send Americans over to visit Tokyo and they have zero problems taking the train. The problems isn't with individual Americans.

Americans don't want to live in dense neighborhoods, so public transit is not viable (the operating costs would be too high). Foreigners are often amazed by the quality of life in American suburbs relative to what they experience at home for this reason. Our homes, cars, stores, cafes, are a lot more spacious for example.