> developing economies are going wireless/fiber and skipping the "legacy" generation, the US should be doing the same with MagLev/hyperloop
Opponents of HSL will not only rally against it, but also kill it by promoting a more expensive solution via another channel. The US isn't going to cut military spending so it can build hyperloop instead of HSL.
The dilemma is no different from "should I buy Product X now, or wait a year for version 2 of Product X", only on a national scale. Needless to say, if you play to this psychology successfully, you can delay a project indefinitely.
Originally anything over 125mph was "high-speed rail" simply because it required new engineering techniques to be developed (existing trains and tracks were physically not engineered to withstand those speeds). As the engineering was developed further, 125mph became old news and the 'typical' definition became more like 160mph [1].
If you compare to highway travel, even 100mph would be "high speed" because people aren't going to drive 100mph on the Interstate. If you compare to airplanes, nothing is high speed, not even maglev. No one is planning to build maglev with a cruising speed of 550mph.
Another important point is that high speed rail is still rail, whereas maglev requires a custom alignment. This could be important or it might not matter at all, depending on where you're building -- e.g. France's system relies heavily on the TGVs being able to use existing conventional tracks (to reach the centre of Paris, and to branch out into smaller cities that don't merit constructing a dedicated line), Japan's doesn't (because the conventional railways in Japan are narrow-gauge).
Likewise, California HSR plans to share most of the peninsula rail corridor with Caltrain. Theoretically it's a win-win (HSR doesn't have to tear a completely new alignment through a heavily-built-up area, Caltrain gets financial support for upgrading its corridor) -- you couldn't do that with a maglev. In practice, the project is not well-coordinated, but see what I said above about Brezhnevian stagnation.
All that said, a train that can travel on both maglev and conventional track would actually be an interesting next step for high speed rail. It doesn't seem impossible.
Opponents of HSL will not only rally against it, but also kill it by promoting a more expensive solution via another channel. The US isn't going to cut military spending so it can build hyperloop instead of HSL.