The focus of this isn’t personal travel, as it is freight, and freight via air is quick but relatively inefficient. Can only pack so much into a plane.
The point of something like this would be to compete with boat, which is still relatively slow.
An underground tunnel, levitated train in a system with no atmosphere would allow insanely fast freight movement and virtually unlimited volume... just add another car.
This idea isn’t as far fetched as some think, but it is an very expensive proposition but very much could be commercially viable.
Air freight is only used for high value items for this reason: pharmaceuticals, small machined parts, electronics.
The point of something like this would be to compete with boat, which is still relatively slow.
For freight of ship size, time does not really matter that much, since there is continual ship traffic into the major ports.
Few projects that require large items like machinery, girders, etc. are conceived, planned, engineered and financed in less time than it takes a containership or a drybulker to go from Beijing to LA (15 - 20 days).
Also, TGV cars are generally 10 feet wide and 75ish feet long, even a train 200 cars long would be dwarfed by a drybulker - by the time the last train arrived to carry the full amount a drybulker would, the drybulker will have already arrived at port.
just add another car.
TGV trains have engine to passenger car ratios of 1:4, and those passenger cars are extremely light compared to a freight car.
You can't have a TGV train with much more than 20 cars that can maintain top TGV speeds.
Freight trains in the US move a lot more weight using a lot less fuel, but they move more slowly.