If you look at the Honolulu transit project (Formerly HART, now called Skyline), I think it shows everything wrong with US transit projects:
1. It goes nowhere useful, only going to a bunch of random places on the west side of Oahu where no one really goes.
2. It was pitched as an economic uplift project, not a transit project. "If we build a train in these largely-ignored areas, it will help the people there!"
3. It took years and years to build, full of cost overruns, because it was also pitched mainly as a job creation project. You can't sell a transit project based on that alone, so instead they're pitched as welfare or job-creation programs, which creates the wrong set of incentives. After all, if the project takes longer, that's more jobs!