I mean, does the population density in the US support bullet trains? I know that both Japan & China for example have large population density within each city (whether you live in Osaka heading for Kobe or from Shanghai to Beijing, you get the picture) plus the governments of both countries invest heavily on the infrastructure including maintenance.
Distance is another factor between destinations, like from Nagoya to Kyoto it’s only 130km (80mi) and the commute by bullet train is 33 minutes while from New York to DC it’s 226mi taking you 4 hours by car but via bullet train, the commute time is less than it would be from driving alone. The cities in Japan are closer to each other by comparison.
China is a large country (not big as let's say like Russia in terms of land size) alongside varying topography and climates (they can still install tracks in uneven terrain but adjusting how they are installed), although their population is larger than the US (they have about more than 1.4 billion people as a country while the US is about 348 million).
The taxes work differently across countries, like in both Japan & China: they have the funds gathered from taxation allowing them to maintain constant upkeep or make further improvements. Well, what does the US government spend their taxes on? That in itself also lies the question whether the taxes citizens are already paying are worth it.
Taxes exist in all countries regardless, as governments need funding to maintain and improve infrastructure, roads, schools, hospitals, etc. The real question is: how is the government using that money? For example, in Japan the reason why public transport is considered reliable is due to their government using people's taxes for upkeep & bullet trains.
Population density is definitely part of it - the only places where it would make sense is on the coasts, and that land is already in use.
If you could get past the land-use issues, where would they run? Boston to Miami is 1500 miles. If a train was built there (again, assuming land use wasn't an issue) - where would it stop? How long could it maintain those speeds?
Anywhere it didn't stop, why would those towns/cities/states support their tax dollars going to such an investment?
Then there's the Final Mile problem - how would people get around once they got somewhere?
I've ridden trains in Europe - they work there for multiple reasons. One is density, but there's also that Europe infrastructure either didn't exist prior to WWII or what did exist got heavily damaged. They had to invest in trains, country by country post-WWII. It wasn't like there was a Grand Europe Train Plan as many countries were still antagonistic at the time, and the train system incompatibilities that still exist reflect this.
What Europe has today is a result of a long, slow development of infrastructure and political relationships.
There's lots more involved, but even these things show how different Europe is from the US - it takes sixteen OECD countries to equal the landmass of the US, divided between 50 states.
Imagine trying to build the Western Europe rail system(s) today if it didn't exist, and much of that land was currently in use for manufacturing or farming.
Apples and oranges.
Why does everyone ignore that America had better passenger rail than Europe till the 1950s/60s?
What killed American passenger rail was the great depression making people unable to buy tickets, and then the federal government eventually selling (really giving) the lines to private freight companies.
That meant faster passenger cars had to pull over and wait on slow freight cars, making driving and eventually flying more attractive to consumers. As a bonus those freight companies wore the rails out faster and never paid to maintain them.
We had passenger train centers all over America (not just the coast) that rivaled modern regional airports, a century ago.
https://en.wikipedia.org/wiki/History_of_Cincinnati_Union_Terminal
We're in a weird spot where it's almost better to "start from scratch" but that doesn't mean we shouldn't.
Again, we've had passenger train infrastructure before...
Terminals like in Cincy brought people in from other Cities and dropped them off at the same place for Intercity trains and even buses.
The same train car that brings you to a city. Doesn't have to drop you off in front of the building you want.
Competent modern public transportation always involves this to some extent
Quick edit:
WW2 was what propped up American rail...
We made a shit ton of stuff for the war and needed to ship materials and product.
That was all freight, and why they had the money/sway to "buy" the rails after.
yeah that's a real issue. you need public transport within a city before you can meaningfully build inter-city rail. because otherwise, you arrive in another city, and now what? you call a taxi? at that point you might just want your own car.