The premise of your second paragraph, that the majority of the country is far away from cities, which means no good chance at public transit, is incorrect: As of 2000, a majority of Americans live in communities of at least 200,000 people, and approximately 70% live in communities larger than 50,000 people.
Ah, but you are assuming that, just because you live in a community of that size, you naturally have good public transit. in my experience, that's not necessarily the case.
To give but one anecdotal example, I'll point out the transportation problem I experienced when I lived in Atlanta area. I lived and worked in the north suburbs of Atlanta and would have loved to be able to take public transportation to and from work, but it simply wasn't viable. I would have had to drive to the train station in my own suburb. We'll call that about five minute. Then I would have to take a train south into the center of the city. I would guess that to be a 30 - 45 minute ride. I'd then have to change trains and take a new train back north into the suburb I worked in. We'll call that another 30 - 45 minutes. I'd then be at a train station a good 3 or 4 miles from the office complex where I worked. With the closest bus stop being 1.5 - 2 miles away from the office. In an area where most of the roads don't even have sidewalks and so aren't pedestrian friendly. All of this to cover a distance that's only 18 miles when I drive it direct.
Public transportation from home to work in New Orleans was just as inconvenient. Not to mention, I wasn't really comfortable with riding the buses in New Orleans.
This is the point that I'm trying to make: just because you live in a population center of 200,000 or more, that doesn't mean that public transportation is available or viable. America has grown up as a car culture, and as such the majority of population centers are very car centric where transportation is concerned.
The less dense the development, the worse the problem seems to be in my experience. Not everybody lives and works in the dense urban developments that public transportation seems to be mostly designed around.
All I'm saying is: if you want Americans to drive less and take public transportation more, give us the egg before you take away the chicken.