Indeed. And moving weight into the wings - preferably, well outboard of the fuselage - decreases the stress on the wing spars.
Shanghai airport to south of downtown was considerably less than 40km - IIRC it was about a 10 minute ride. We looked at the regular subway which did a suburban route and from what we could tell that would take well over an hour with about two dozen stops.
It was so incredibly smooth a ride that I looked out the window half-way through to find the whole world had tilted - the curve was so smooth you didn’t notice the banked turn.
Washington-Baltimore is the first logical step in a link to Boston through several major cities assuming someone has the will to spend money. Various administrations have dangled the prospect they yanked away the funding over the last two decades.
Mag-Lev, even more than TGV, needs a support structure. To make good time, it needs a minimum of stops. The surrounding transportation from those stops needs to be sufficient that people would find the whole trip convenient.
For now, it seems short hop commuter aircraft feeder routes an appropriate option, and the really short ones can benefit from electric aircraft. For trips of 5 hours or less, TGV between cities may be an option.