I think self driving cars are important for a couple of reasons:
1. Demographics - Aging population needs transportation. God knows we certainly don't need really old people driving themselves. We got a taste of the future in West Portal in that regard not long ago.
2. Human Capital - The US has pretty much demonstrated that there is little desire to import low skilled labor. Where do these theoretical Taxi drivers come from? Or welders or plumbers. Labor is going to become increasing expensive no matter how you slice the pie.
3. Younger US citizens are going to gravitate to non-manual labor jobs. It is not just that every one is being steered toward college. Physical labor (trades) take a toll on the body. I know - I have work in them - and you quickly extrapolate what that will be like when you are 50.
Public transportation solved this before cars were commonplace. Implement ubiquitous and free public transportation in every urban center (where 80% of the American population lives [0]) and you'll save billions from not having to manufacture (and store!) cars.
0: https://www.census.gov/programs-surveys/geography/guidance/g...
For public transportation to be broadly appealing it has to be clean, safe, and fast. Which means that you have to prevent people who are antisocial (playing loud music, etc.), violent, or just have terrible hygiene from boarding. You can't expect the bus driver to double-task as a security guard, so you have to somehow figure out a different way to implement security enforcement on the vehicles. You also may have to be ruthless in optimizing overall transportation value, of which speed is a factor, which may mean cutting some stops.
You have to have the political will and support to do all this even as the almost inevitable controversial videos hit social media: people being manhandled by security guards while protesting their innocence, people complaining about how there used to be a stop on their street but now it's gone, etc.