There are only two profitable high-speed rail lines in the ENTIRE WORLD. One in Japan and I believe the other is in France. High speed rail just doesn't make sense especially in the spread out urban centers that make up the US. The last mile problem is huge.

Someone commented on the airports being near capacity. That's only because our air traffic system is horrible. If they updated the system and automated much of it, we could drastically increase capacity since the planes could fly straighter routes instead of the current zig zap pattern and fly much closer together safely. Sadly the air traffic controllers union won't allow the changes since they'll lose jobs in the productivity increase.