Public transit absolutely could work in America, but we would need to change how we design our cities as well as how we live. Many Americans live in sprawling suburbs where public transit is just not realistic. In places that are densely populated public transit does exist and functions well. The issue is that we build sprawling cities with massive suburbs filled with single family dwellings each with their own yard and space. We do the same thing with stores by having hugely sprawling shopping areas (most of which is separated by massive parking lots). It's a chicken and egg problem. You won't convince people to give up cars until they can realistically walk or use public transit to get where they need to go efficiently, but you also can't make things efficient and compact while there is a huge demand for car storage. And beyond that, I think culturally most Americans don't want to live in densely populated areas. Americans culturally put a high value on personal space and that extends to dwellings. Sure there are definitely people who want to live in an urban center, but the "American dream" is a house with a white picket fence and a dog, and until culturally the desire for that changes, America will be a car-centric society as a whole.