The reason people fly domestically in the US is that non plane travel is both slower and more expensive than flying.
“High speed rail” is less than half the speed of a 787 say, so a beat case scenario would make it an 11 hour trip. Except that best case scenario would require the route have no stops and be essentially flat and a straight line with essentially no stops. I would guess in practice a best case high speed rail would have that be in the order of twenty hours.
It also wouldn’t stop the TSA wanting to have pervert scans and mugshots. The moment any significant amount of people started using it, the TSA would want to “protect” us.
What trip is "it" you're referring to that would take 11-20 hours?
The busiest domestic US air route is Las Vegas - Los Angeles, which takes only a bit more than an hour. There is an idea to connect them by high-speed rail which would make the trip 3 hours: https://www.hsrail.org/brightline-west/.
That would be faster than driving, which lots of people do as well.
SFO->NYC is a 5 and a half hour flight, which is 11-20 hours on high speed rail.
That's obviously an extreme example. But yours is an extreme as well: the busiest domestic flight air might be LV<->LA, but that doesn't mean it's a significant amount of domestic traffic.
Now high speed rail between some of the major centers is obviously something that makes sense, but it also _only_ makes sense for major centers. So the myriad routes regional airlines make possible (and that I suspect make up a significant proportion of total US air traffic) are of questionable value for high speed rail, if high speed rail were even possible.
You mention people driving to Vegas. People are driving to Vegas from LA because it's cheaper than flying, and LA->LV isn't even an insane drive: google maps says it's four hours which is about as long as I spend commuting each day in the SF Bay Area, so that seems reasonable. I'm going to say my google "la to Las Vegas drive" is optimistic and say in practice it's a 5 hour drive, but that's only two hours slower than the high speed rail under that pessimistic view, which itself is 1-2 hours slower than flying. At the same time flying is cheaper than high speed rail - I looked at a bunch of prices on Eurostar from London to Paris and Brussels (because la->lv be further than Brussels but less than Paris) and the cheapest prices I found were consistently more expensive than flights. Now I can't see why we would expect high speed rail in the US would be cheaper than flying when in Europe rail is more expensive than flying, and existing non high speed rail service in the US is already more expensive than flying.
> the busiest domestic flight air might be LV<->LA, but that doesn't mean it's a significant amount of domestic traffic.
There's apparently 352 flights between the cities each week, I would say it's pretty significant.
> People are driving to Vegas from LA because it's cheaper than flying (...) I can't see why we would expect high speed rail in the US would be cheaper than flying
That's partly a political decision. Highways get lots of public funding, there's no reason rail shouldn't get funding too, if that's what's necessary to incentivize using it over flying. That's the direction Europe is going in (in addition to taxing air travel due to the negative externalities it's causing).
“High speed rail” is less than half the speed of a 787 say, so a beat case scenario would make it an 11 hour trip. Except that best case scenario would require the route have no stops and be essentially flat and a straight line with essentially no stops. I would guess in practice a best case high speed rail would have that be in the order of twenty hours.
It also wouldn’t stop the TSA wanting to have pervert scans and mugshots. The moment any significant amount of people started using it, the TSA would want to “protect” us.