Why not trains

I had the occasion to visit the museum in the old train station in West Yellowstone, Montana a few weeks ago while on vacation. There used to be trains there, bringing early visitors to Yellowstone National Park. Now, no trains. Why?

Trains are the most efficient form of long distance transportation. In preparing for my vacation, I looked into the train alternative as time wasn't much of an issue. I quickly realized trains are a more expensive alternative than airplanes, if you can even get there from here. Why is that, and why is it so? Trains are the most enery efficient form of long distance transportation, so why does it have to cost so much?

Maybe it's a chicken and egg thing. If there were passengers to fill them would there be more trains. If there were more routes, and prices were cheaper, maybe there would be more passengers. If trains were half as fast as airplanes, maybe there would be more passengers.

Maybe we need some high speed trains between major metropolitan areas, with local hubs to more places. Europe has that, Japan has that, why doesn't the US have that? If I could get on a train and go from Dallas to Los Angeles in 12 hours or less, I would probably never fly again unless going over the ocean.