Ask Lemmy

There are a few different reasons why.

• The US already built up its rail network around low speed trains. Those tracks aren't suitable for high speed operations, and can't be modified easily for high speed operations. It's not just the tracks themselves, it's the actual paths and bridges and road crossings. If a turn is too sharp, it can't be taken at high speeds, and the actual curves in the path didn't anticipate that one day trains would be fast enough to need more gradual turns. So any new rail would have to buy up the land rights with any new pathway, and that is going to be inherently expensive in the corridors dense enough to where there might be demand for passenger rail.
• Rail crossings have to be designed for high speed rail, as well. There are safety and congestion concerns, so many high speed rail projects are required to build more grade separated crossings (bridges and tunnels), which significantly increases construction costs.
• Rail has to compete with air travel and highway travel, in a country rich enough to have lots of people who can afford to fly, and where car-based highway systems are convenient and cheap. Basically, there's a sweet spot of around 200-400 miles (300-600 km) between cities where it's far enough that a car is inconvenient and close enough to where trains are competitive with buses or airplanes.
• Along those lines, the US actually has pretty cheap intercity buses that use the existing highways.
• Unfortunately, the city pairs that would have the highest intercity passenger demand also tend to pass through a lot of other cities. If you're going from DC to New York, the most popular rail line in America, you'll pass through Baltimore, Wilmington, Philadelphia, and Trenton, each with their own powerful politicians who would push to make sure the train actually stops for them. This is part of why the Acela, our fastest passenger train, takes 190 minutes to travel 226 miles between DC and New York, averaging only 70 mph (115 km/h) despite being capable of reaching top speeds of 160 mph (255 km/h).
• Most rail in the United States is owned by freight/cargo train lines. The passenger network has to lease spots and is lower priority than freight. This leads to scheduling issues, including unscheduled delays.
• Americans are just really bad at constructing big public works projects. Our dams, bridges, tall buildings, rail, highways, roads, power plants, and all sorts of other big projects are almost always behind schedule and over budget.
• The less populated areas where it's cheaper to acquire land rights also tend to be more environmentally pristine, which means there are environmental concerns around projects like these. In our political system, Republicans are much more likely to ignore those environmental concerns, but they use that political clout to build highways and oil pipelines, not passenger rail. Advocates for passenger rail tend to also be more environmentally conscious, so the environmental concerns do tend to slow down any proposed rail project.

There is high speed rail called Brightline in Florida between Miami and Orlando, with the longest segment operating at 125 mph (200 km/h), and some of the more populous segments operating at 110 mph/180 km/h or 80 mph/130 km/h. It tries to manage those tradeoffs on all new track dedicated to it. But the company is struggling to make money.

There's a whole saga in California in that the proposed high speed rail project is decades behind and still bogged down, and has examples of all of these problems. The route it takes to connect the two largest cities on the coast (Los Angeles and San Francisco) goes through the inland central valley, to service a bunch of other cities in between. Bizarrely, phase 1 of the project will only serve the relatively low density, low population cities in the Central Valley, without connecting either San Francisco or Los Angeles. Some segments are to share rail usage with lower speed trains, complicating scheduling and risking delays. The environmental debates have slowed things down, as well.

Watch what happens in Texas with its proposed high speed line (bogged down in political infighting), Florida (see above, already built and operational, but facing serious financial concerns about its ability to continue), and California (see above).

I think we'll eventually see some projects push through, especially if jet fuel gets more expensive than electrical grid power. But for now, America is uniquely hostile to passenger rail, and increasing high speed offerings isn't necessarily going to induce enough demand for these projects to become economically competitive with other forms of intercity transportation.