I didn't know that they were overlooked. The railroads united the U.S. in ways that had never been done before. In U.S. history troops were first brought to a major battle via train early on in the American Civil War. They were rebel reinforcements at the first battle of Bull Run and the result was a major southern victory. Later on in the war you have what are known as 'Sherman's neckties'. This saw to the destruction of a lot southern rail line by super heating and twisting the metal. All of this is in Ken Burns' marvelous documentary series on the American Civil War.
After the American Civil War plans were laid to get more people to move West. Part of these plans included having East and West united by rail. Certainly the 'Iron Horse' changed the way of life for many of the plains Indian tribes. I have read about so-called game hunters shooting buffalo from moving trains, leaving the bodies to rot.(Not the railways finest hour.)
In the 1920s and 1930s films you do see some American pride in the new super trains that were Art Deco by construction and design and looked like fantastic rockets or bullets on rail. One of the Thin Man movies featured travel by train.
I remember the Adventures of Superman television show in the 1950s. Superman not only was faster than a speeding bullet he was also more powerful than a locomotive (a train). Also in the 1950s you had Casey Jones on television. Who can forget Casey Jones (starring Alan Hale) at the throttle of the Cannonball Express? Then in the 1960s there was Petticoat Junction. The Shady Rest Hotel wouldn't have gotten much business without the Hooterville Cannonball. The first episode of The Wild Wild West had travel by private train as did every other episode. When they recently made a Wild Wild West movie the private train once again was featured.
Possibly what has been forgotten by some though not all Americans are those who died while constructing the railroad that linked East with West. There were many Chinese out from San Francisco involved as well as African Americans and Irish immigrants. The use of Chinese laborers is touched upon in the '70s television series Kung Fu.
All up, I'm not sure who it is that overlooks the larger picture of the railway in U.S. history. I'm an Australian and I know how the railway helped to unite my country. I thought, thanks to the richness of information out there, that Americans would have the same understanding about their own country.