Why Americans are so attached to slow moving transport - those speed limits without any reason (since you build roads devoid of turns) and the neglected trains - is somehow beyond me. Is it the relative cheapness of inland flights? The country certainly is big enough for flight to be viable.
A lot of us aren't, actually. If I could trade in my car for a reliable public transportation system, it would have already been done. The 4.5 hour drive from my university city to my hometown is mind-numbing, and that's not even that bad. As for the answer why our transportation system remains as it is, Kyoto Kid gives a great history. From what I understand, the following also contribute:
1. The fear-mongering media has everyone from the right side of things up through many of the moderates fearing all things socialist to the point of hilarity or depression--depending on your outlook. That includes functioning public transportation.
2. Most of our government officials in the House and Senate are in the pockets of lobbyists and/or only concerned with getting elected next term, not actually governing. They're looking to make oodles and oodles of dollars, regardless of what happens to the rest of the country. This also results in any bill getting tied up for about forever, or never even putting on the pretense of going through committees.
3. Out of sight, out of mind mentality. The lower working class and university students often rely on trains to get where they need to go, at least around my campus. But, we're a blind spot in reality, you know.
4. People are lazy. They also resist change with amazing stubbornness.