The majority of Americans trying to get from A to B are driving less than 60 km/day, a distance which trains can cover pretty damn fast.
For longer travel you could have high speed trains on both coasts' corridors, very few people are traveling NYC -> LA on a regular basis, most people will travel on their surroundings (500-1000 km).
You could have a multimodal system covering the most important urban corridors, rural places would almost always need cars due to the low density but it's a big fat lie that the USA is car-centric because it's the only solution for its size.
The only reason you are a car-centric country in 2024 is because of incentives for the car industry, the design of your cities being stuck in car-centric mindset from the 1950s-1960s.
You don't need to give up cars completely, you just need infrastructure to not require a car for people traveling around your major urban centres. High speed rail corridors between Seattle - Portland - San Francisco - Los Angeles - Las Vegas - Phoenix, another corridor from Boston - NYC - Philadelphia - Baltimore - DC branching out to Pittsburgh - Cleveland - Detroit - Chicago. With those you cover a lot of the major economic centres.
China is also massive and they've managed it.
Except for some new shiny skyscraper, the USA feels more backwards each time I visit, like the country is stuck in the 1980s-1990s and refuses to be updated to how a modern country can be in 2024.
This is obviously incorrect from a quick glance at history.
Long distance travel in the US used to occur primarily by train. Short distance travel used to occur by walking and streetcar.
Now, with suburban sprawl (a relatively recent phenomen), we have something we could call medium distance that is filled in some areas by light rail.
We now also have other options for very long distance travel: aircraft.
In my small town, we have roughly 125 people. We are, roughly, 35 minutes away from the nearest grocery store, or about 40 miles. Too long to walk or bike in a reasonable time. You could use a motorized bike but the amount of food for a family would be unwieldy. The only viable solution is to drive via car, because you need the trunk space. And both options to get there require roads. Now, let’s suppose we magically replaced highways for rails. What happens is simple: either the government is bleeding immense amounts of money orchestrating train rides to places where no one is regularly using it, or certain less populated areas are underserved.