A major problem with train systems in the United States (and this is both short and long haul) is that almost the entire country is sprawl - built around the automobile.
In dense environments (China and the north-east coast of the US (which has Acela), it's great to take a train into the core -- you beat traffic and are near your destination.
In sprawling environments (like most of CA), the benefit of ending up in the core is so much less (possibly even negative). Lower probability you are near your destination. And if you need to drive, now you are in a much worse situation (higher car rental prices due to high land values, you are stuck in traffic trying to leave the urban core, etc.).
In other words, even if you had a train, most individuals still will prefer driving (you have a car with you) or flying (faster than trains) -- killing the ROI on building the train in the first place.