Rail is very nice once you have it. The problem is that building it is a very slow and complex process. My home country (the Netherlands) has a single high speed rail connection to Paris. Very nice. It took decades to build. Had many political scandals attached to it (some of which are still unfolding). Cost many billions more than was budgeted. Had a string of bankruptcies associated with its exploitation.
But it's very nice that you can travel from downtown Amsterdam to downtown Paris in about the same time it takes to get to and from both airports and fly there. You don't save/lose a lot of time (or money) but it's just more convenient.

It's a great example of why building new rail is not that common in either Europe or the US.

In general even modest amounts of rail tend to cost billions to put in place. E.g. recent subway line extensions in Amsterdam, Berlin, New York, etc. cost billions each. It's so expensive that it is typically big news when it happens. And it doesn't happen a lot. Rail in Europe is used very intensively but there is very little added to that network at this point. Most of what is there, has been there for a long time. Munich and Berlin gained a new high speed rail connection just a few years ago. That was big news. Planning for that started shortly after the wall fell, 30 years ago. That's how long it takes.

So, for the US to start building rail now, it would likely be stupendously expensive, take decades to complete, and have probably very questionable value relative to other solutions. Even just figuring out where to put it would take a very long time and involve fighting local land owners throughout the US.

There are other things the US could do, including a few new solutions that are changing the economics of transport (and thus remove arguments for investing in rails).

Basically, the premise of rail is that using it is cheaper than burning a lot of fuel to drive (or fly) people around. Except we are switching to electrical cars now which cost typically about at least 5 times less to operate with likely further improvements over time. And they can use sustainable sources of energy. Electrical buses are already a thing. Several Chinese cities use them exclusively by the tens of thousands each. And cities world wide are starting to deploy them.

And even electrical planes are being considered (hybrid and battery) and likely to be a thing before any significant amount of new rail would be ready for use.

That changes things. Flying is dirty, not that expensive, but convenient. The US has a lot of domestic flights for that reason. A few decades from now that could be a lot cheaper, clean, less noisy, and even more convenient. Guilt free, cheap, clean transport is becoming a thing.

And that's before you consider autonomous vehicles. Drivers and pilots need salaries. So that raises the operational cost. Self driving buses might become a thing pretty soon. You don't even need level 5 autonomy for that because they drive fixed routes and schedules. Many cities even have dedicated bus lanes. So, self driving, electrical buses could be a cheap and viable way to ferry people around. Autonomous flying electrical vehicle startups are already flying some prototypes around. Waymo already has driverless vehicles on roads in the US. So, it's more a question of when than if that will happen. The cost for autonomous vehicles is going to drop over time as well.

And it doesn't require a massive investment in infrastructure. And you can flexibly create routes to just about anywhere it makes sense to have them. And you can take self driving taxise everywhere else.

So why build rail when we can do and scale all of that in the time that it takes to build a lot of new rail that is only usable exactly where you build it?