The US has an extensive rail network, but it's main purpose is for freight transport. There is a lot of freight train traffic in the US, and so many Americans live and work near train tracks, cross them during commutes, are used to interacting with trains. Just not riding on them.
Subways and other forms of light rail are common in large cities and have a lot of ridership. But these are not typically very plugged into broader rail network. Only a few of the major cities like Chicago or New York have shared stations for local and non-local train service. Taking a train between metropolitan areas us very uncommon outside of the east coast corridor.
For my part, I travel between Minneapolis, Milwaukee and Chicago quite often. I've done it once all by train, just to see what it was like. I can park my car at the Mall of America, take the light rail over to the Amtrak station, then the train down to Union station in Chicago, then a commuter train out to my destination in the suburbs. All told... it ends up taking 12+ hours, and costs about the same as the plane ticket down there. The Megabus is way cheaper, and takes about as long. I could just make the 6 to 8 hour drive, which gives me maximum flexibility. Passenger rail face some stiff competition.