When I was living in the SF Bay Area, I took a class on 'Homelessness and Public Policy' from an SF college. My recollection: There were about as many homeless people in SF at that time as in NY and NY is quite a lot larger, population-wise. That is probably part of why you see so much crap (literally and figuratively, I guess) on SF public transit.
I would be all for improving public transit in the US. I currently live without a car and I don't want to ever go back to owning a car or driving one. Yet I basically don't use public transit because, where I live, 'you can't get there from here'. (Ex: There is a bus stop maybe 15 minutes from my apartment and a bus stop maybe 10 or 15 minutes from my office. You can't get there from here by bus, except possibly by going an hour downtown, changing buses, and coming back. I can walk it in less time than that.)
I would be all for improving public transit in the US. I currently live without a car and I don't want to ever go back to owning a car or driving one. Yet I basically don't use public transit because, where I live, 'you can't get there from here'. (Ex: There is a bus stop maybe 15 minutes from my apartment and a bus stop maybe 10 or 15 minutes from my office. You can't get there from here by bus, except possibly by going an hour downtown, changing buses, and coming back. I can walk it in less time than that.)