I'd argue that the cost/benefit of a totally non-interoperable system with an expensive, and at present bespoke, technology is questionable. Ditto hyperloop."Super expensive and impractical" - The same thing could have been said when the Interstate Highway System was proposed and the early stages were started. The same could have been said about efficient airports with equipment in the air traffic control facilities.
If the Gov't officials had taken the same view and direction with the Interstate System and airports that they have taken with passenger rail (or all rail,for that matter) we would still be driving on dirt roads and using grass runways at small private airports.
The rail system is really no more expensive or impractical then most of the other infrastructure in the US ... just not as popular amongst those who control the purse strings.
The difference between either of those and the Interstate Highway System is that almost all personal vehicles could use it as-is. Note that in most of the world, HSR tends to start out with various chunks of lines being upgraded while (for example) conventional tracks are used for the approaches to major cities, at least to start with. France is a pretty good example of this.
Having to basically start "fresh" with a system that's 150-250 miles long and that can't "play well" with others is tricky (and requires a lot of up-front investment for a dedicated ROW, stations, etc.). Shorter "demonstration" systems can also end up with highly outsized costs (e.g. the estimated costs of the NEC Maglev run, at the low end, in the $250-400m/mile range. NGL, I would expect that cost to go up...costs always seem to.).
As to some of the hyperbole in here...no, what we would likely have is a series of partially-disconnected but decent highway systems (some financed by specific interests, some financed by businesses wanting links to elsewhere, and some financed by state/local governments, and plausibly some random connections thrown in when enough business interests decided that a shipping link made sense) in line with what was evolving in the 1920s and 1930s (e.g. the Baltimore-Washington Parkway was being developed from the 1920s). By the same token, you'd probably see decent airports in major cities...but that would be about it: Either an airline cabal would get together and build the airport, local interests would do so, or it mostly wouldn't happen[1].
Also, don't forget that large-scale federal investment in highway infrastructure as an end (versus as a means to an end, as was the case with a number of Depression-era projects) was very much a lagging indicator: Household automobile ownership was up to 60% as early as 1929, and the Interstate Highway System didn't sort out for another 25 years.
The sad thing is that I'm not entirely convinced that the resulting world wouldn't be better than what we have now in many places...we'd at least have less suburban sprawl and a bunch of cities wouldn't have been trashed in the process. Even if "better" would very much be subjective, it would definitely be different...but again, I'm not sure you could argue that it would be objectively worse.
[1] Of course, a major asterisk here is that a lot of the airports that popped up in the 50s and 60s were ex-military airfields from WW2. Orlando is a pretty good example of this. Others resulted from post-WW2 land transfers (Newport News' airport comes to mind) and still others were probably helped out by performing "double duty" for the military.