Mythbusters already tried this experiment, and they were able drive from SF to LA door to door in the same time it took to fly, end to end, 5 - 6 hrs.
If you've ever traveled between cities in France or Japan on high speed rail you know its infinitely better than an airport. I can arrive at an Shinkansen 5 minutes before departure, travel a similar distance between SF->LA in 2.5hrs or less, in a super comfortable train, that I'm free to walk around it. At my destination, getting to/from the high speed rail is also super-convenient, hassle free, doesn't require driving, and overall, is cheap.
Short distance air travel is majorly annoying no matter the cost. I hate the airport in/out experience.