People keep wanting these long as fuck HSR routes and, well, that's really not the space HSR fills in transport infrastructure. HSR generally replaces short-haul airline trips, which is why it would be YUGE for LA-SF, the TX metros, etc. But it still tends to lose out to airlines on long-haul trips because, eventually, jets are just faster. China does do these crazy long routes, and I'm not really sure why, unless their air infrastructure is really whack or something. I THINK that their longest lines still fulfill the role of replacing short-haul flights, it's just that it didn't make sense to separate the alignments when it's all along the same line anyway.

Basically, HSR is a huge PITA to build right, a well worthwhile PITA, but a PITA nonetheless. That makes it really expensive on the frontend, on top of not being competitive with air over very long distances. What would be more realistic for long-haul rail transit would be something closer to Brightline, which isn't true HSR. They use a different FRA rail class than true HSR, and don't achieve the same speeds, but it's still reasonably fast (in the triple digits), doesn't requires extremely specialized stock, and it's a lot cheaper to build. Replacing Amtrak's long-haul lines, like the Coast Starlight, with dedicated class six or seven alignment would mean that they could reasonably sustain about 125 mph. It's currently a 36 hour trip (notably, 2x the time to drive from Seattle to LA), but that would bring it down to about (1,135 mi / 125 mph, mi cancels leaving us with) 9 hours. I can't really set aside two days to take a train to Seattle, but I could plausibly set aside 9 hours, especially given that it's a little over half the time to do the drive. Heck, you could even make it a sleeper train. I'd do that over an airline in a heartbeat. The California Zephyr runs from Sacramento to Chicago, IIRC, and takes about a week. On its own class 7 alignment, that would be (2045/125) just 16 hours. That's a hell of a lot better than a week, and half the time of driving.

So, HSR for long distances isn't really that good or valuable, IMO, but that doesn't mean that we can't do highER speed rail for long distance travel.