Well, keep in mind some of those cities are thousands of miles apart - New York to Los Angeles is about 2,800 miles (4,500 km). While I believe we should have a robust rail network, it's tough to justify it for that kind of distance given that planes are so much faster.

In my mind we'd have a three tiered approach - cities would have subways, busses, and commuter rail options. Nearby cities, say, less than 500 miles (800 km) apart, would have high speed rail connections. Longer trips would be handled by airliners. Because, lets face it, no one is going back to land transportation between New York and LA - even at 250 km/hr, a train would take 18 hours - and that's nonstop, whereas a flight is 6 hours. Few people are going to be willing to triple the travel time like that.

So, in my world we'd have a cohesive transportation plan that focuses each mode for what they are best at. I'd still want a good nationwide rail network as a fallback (in case of, say, a 9/11 type event where the airline network is shut down), but I think it has to be bigger than just rail.

This would reduce the issue of a busy air traffic network as well, by removing short haul flights in favor of trains.