I think the biggest challenge to rail in the US is just how huge the US is.
Take a common train ride in Europe: Paris to Berlin. You've actually traveled less distance than from New York to Chicago, and it took 8 hours to do so.
In fact from Paris all the way to Moscow is much shorter than from LA to NYC.
Without some amazing new tech in rail, I doubt it'll ever be a popular alternative in the US to flying (other than intra-regional trips).
Take a common train ride in Europe: Paris to Berlin. You've actually traveled less distance than from New York to Chicago, and it took 8 hours to do so.
In fact from Paris all the way to Moscow is much shorter than from LA to NYC.
Without some amazing new tech in rail, I doubt it'll ever be a popular alternative in the US to flying (other than intra-regional trips).