Problems with high speed trains...

1. Energy Efficiency: Slow trains are very efficient. But what if you flew your jet at an altitude of 2' MSL at 300 mph? What kind of fuel burn would you see? Anything that fast creates a lot of drag at sea level, regardless of whether it has wings or not. Electricity is better than liquid fuel, but has additional rail infrastructure costs.

2. Infrastructure: The current rails won't work, they will need new ones and they will have to be straighter. The NIMBY's won't sit still for that, especially in the highly populated areas where rail might make sense.

3. Security. Trains have all the same issues that airplanes, plus one extra. If the airplane is properly secured on the ground, it is safe once airborne (no, MANPADS are not viable anti-airliner weapons, they were not designed for that). A train is vulnerable over it's ENTIRE route...bombs, mortars, rockets, etc. Hell a cinder block thrown on the tracks would destroy a 300 mph train (KE = 1/2MV^2)

It might work in some highly dense areas (NE corridor), but they will have a hell of a time building the tracks. Airplanes just work better for a nation as large as the US. We do need cost-stable, renewable, carbon-neutral fuels though (biofuel).