You can't just appeal to Elon Musk assuming he knows all and has figured this out.
Have you ever travelled beyond the US and seen an international subway system? I haven't travelled much but there are some amazing systems out there. Japan had 130mph bullet trains in 1964, can you believe that? They're maxing out at 375mph with levitating trains now, and they actually exist unlike Elon's ideas. Why do you give ideas more credit then something that already exist and work brilliantly?
Last year Japan Rail issued an apology because one of their trains left a station 20 seconds early [1].
Even in my town of Sydney, with huge suburban sprawl, we have beautiful, quiet, air conditioned, double decker trains that go to most suburbs and cost $1.50 to $4.
The future has already arrived, the US just doesn't have it yet.
https://mobile.abc.net.au/news/2017-11-17/japan-train-apolog...