There are already places in the US that can financially justify Japan-tier high speed rail (specifically the northeast corridor), but Connecticut simultaneously wants high speed rail through the coastal towns and opposes the land acquisition required to get adequately straight tracks. If American politics is unable to get out of the way in such a slam-dunk case for rail, what hope is there to bring public transit and urbanism to all of the car-dependent suburbia in the rest of the country?

I'd say the success of Florida's Brightline, from Orlando to Miami, says that it's viable (or that the people in Florida are crazy), especially since it was finished in 2018 and not 1820.