To quote one of the commenters in the HN discussion:
You will have to solve the epidemic of homelessness and crime in high-density areas of the United States before people will accept using mass transit. I fully support doing so - I would for example support a national project to build cheap concrete housing for all who need it - but that's the barrier.
I've straight up had people tell me that even if Public Transportation were convenient and consistent, they still wouldn't take it because Public Transportation is famous for being pretty dirty and having large potential for crime.
I'd like to have some sort of quick, easy solution, but I think changing that perception is going to take time, and the time the US is taking to revitalize Public Transportation isn't making that happen any faster.