America's transportation system is stuck in the 1950s because the collective mindset of our power structure--and the people in it-is stuck in the 1950s.
Think about it. The nation is currently run by Baby Boomers, who in general have been a conservative generation as adults. Not necessarily conservative in the political sense--though they were the driving force behind the "Reagan Revolution"-but conservative in the sense of being utterly conventional in their preference of aesthetics and structures for daily living.
The suburban world of Ozzie and Harriet and Leave it to Beaver is what they lived and idealized while growing up. In the Post WWII 1950s, the suburb was the future, the car was the ultimate symbol of status, sex and freedom and the city was in its rear view mirror. Metro rail was being ripped up and replaced with four lane highways to service all of the new developments of little boxes made of ticky-tacky that were sprouting up on farmland.
When the Boomers themselves became more established as adults, they put the suburban dream into overdrive from the early 1990s through 2007.
The push, particularly among the younger generations now for rail, urban life and living options and high-density mixed use development is falling on deaf ears because what they want isn't what the Boomer "powers that be" want. Our leaders have little concept of these things as being good and desirable. Even worse, they may view them as a threat to the "American Dream" and way of life that they grew up with and still believe in, as they see it (This explains Kasich's governorship in a nutshell).
The solution? A generational shift in the halls of power and policy. It's actually happening now, but many of those in favor of maintaining the status quo will not go quietly. Public outrage at pump prices above $5.00 a gallon might help them along.