Since people are talking about them again and being dumb as usual, trains don't actually have to be that SUPER to be competitive with flying over certain distances. Top speed sound exciting, but it's average speed that matters. The problem with the Acela isn't that it "only" gets to 150 MPH, the problem with the Acela is it only travels that fast for very short distances.
Average speed of 100 MPH means you travel 300 miles in 3 hours (this is advanced math, so pay attention). That's Philly to Pittsburgh or St. Louis to Chicago. That beats driving and it's more than competitive with flying given the various inconveniences associated with airport travel (security, more affected by weather, flight delays because airlines suck generally, airports are not in population/employment centers, etc.). Get that average speed up to 150 and (again, advanced math) and that's down to 2 hours and is going to be competitive with private jets, overall time wise.
It's a big country and trains from NYC to LA, even if SUPER, will never be competitive with flying. Nor will NYC to Chicago, really, though it would be fast enough that some people would take it.
If I ran the zoo with a fixed budget, I'd spend the money on 1) intra-city transit enhancements, 2) upgrades for inter-city rail (curve straightening, double tracking, etc) and frequency enhancements that would improve service greatly without large amounts of money. But, really, rail corridors between city pairs under 300 miles apart can be desirable if we manage to get those speeds up to (checks notes) 1910 levels. Any city pairs under 500 miles would be that way if the trains go just a bit faster. True SUPERTRAINS are great, but even then it isn't precisely the top speed of the train that matters, but the average. If the train sits in an intermediate station for a 20 minute stop, or has one 50 mile "slow" segment, then the gains from those top speeds disappear pretty quickly.
