The problem today is that it's an order of magnitude longer. Chicago to LA by airplane is 4 hours. Chicago to LA via Amtrak is about 56 hours. I don't know that high speed rail is going to fix that problem, sure it might get it down some, but even a 24 hour train is six times longer than flying.

I say this as someone that takes Amtrak at every opportunity because I enjoy trains and want to see them become viable for more people.