The USA's westward expansion was indeed facilitated by the timely development of railroads, and so many of the cities were built around the ability to haul freight and service depots along the rail lines, much like ancient cities sprang up alongside rivers and bays because of boat shipping.

However, the United States is also a nation built upon the motor vehicle, and our much-vaunted freeway system here was built deliberately as a national defense measure that could easily move materiel and troops between cities and states, in the event of a domestic invasion or future wars on our own soil. The freeways enjoyed deep investments also due to commercial utility, and again, many cities and habitations sprang up at the nexus of various freeways, as truck-based shipping could service them as well.

I think one of the main obstacles to rail lines in the United States is our car-centrism, and many motorists of any socio-economic class really, really hate trains and public transit of any kind, and any other type of transport that may impinge on their freedom to drive wherever they want on as many highways as possible.

Therefore it is extraordinarily difficult for railways to get good rights-of-way. Amtrak is a redheaded stepchild. Commuter rail may be better respected in places where it was established, like the Eastern Seaboard, but if I asked any voter or motorist here, they would be voting against any sort of rail project whatsoever.