It really is a tough problem I think.

If you put in high speed rail from my small town in the Sierras down to a nice beach, I'd be all over it. As you probably know, there's really not much in the way of point to point mass transit needed. Vacations are well served by air and car, commutes are everywhere to everywhere within urban and suburban areas.

In addition, there's the personal security angle. The US ain't Japan.

I figure if people wanted mass transit to be a thing, they'd start by heavily subsidizing comfortable buses. Super scalable, pretty quick, relatively cheap.