Serious question but is there a reason more isn't invested in public transport? I've only ever lived in the UK before Tokyo but America is rich enough I don't see why they can't do what those places do.
The major reason seems to be a lack of cultural support. Despite everything, people still largely dislike the idea of public transit. I read a very good article that said to generate interest, transit must preemptively provide better service... its a catch 22
Simple: sprawl and ultra low density. Public transport thrives in areas where a single bus stop serves hundreds or more of people, but in rural areas it's cost-prohibitive.