For reference, Boeing 747 average speed is 909 km/h (565 mph) with a top speed 986 km/h (613 mph). However maglev train saves time on landing and coordination makes it faster compare to air travel.
How long do you have to wait if you miss your flight? How certain are you of an on-time arrival? How early do you arrive at the airport, to make sure you'll catch your plane?
There is no technical reason airplanes couldn't do this for any city pair. There are reasons that airplanes don't operate this way, but they are not because it is technically impossible. Politically you can't get rid of the security theater, and yield management probably is the most profitable way to run airplanes, but both could change if we wanted to.
Also, a new station at the center of a major city requires a tremendous amount of investment and work, and some new stations may end up outside or far from the center so you'll need time to get to the place you go anyway.
Such projects are likely easier in China where the government has very effective power, not that easy to build in city centers in many other countries.
I think acquiring all that land and getting it through environmental review is pretty much impossible in the US.