The french railroad SNCF is broke.
Broker than AMTRAK. And the TGV is the biggest money loser in the system. Even though it is relatively expensive.
The French are very good at technology and research but weak when it comes to putting that technology to efficient practical use.
All the experts agree that the TGV is superior to the Japanese Shinkansen technically. However, it is almost never on time, especially during peak travel periods. Whereas you can set your watch by the Shinkansen.
One of the "advantages" of the TGV is actually one of its handicaps.
The Shinkansen requires special rails so no other trains use the Shinkansen rails. They are generally elevated, and so the train has no traffic problems whatsoever. There is even a seperate train station only for the Shinkansen.
The TGV on the other hand runs on the same rails, and uses the same station as all the other trains. This was initially seen as an advantage because it saved a lot of initial cost.
However, the Shinkansen can run like a metro. It leaves a station, speeds up to its optimum speed, and stays at that speed until making a smooth computer controlled slow-to-stop for the next station.
But the TGV, as it enters a town, must slow down to a crawl because it is sharing the rail network with all the other trains. And it often has to wait for several other trains to leave the station before it can leave, and even then it cannot accelerate until leaving the city grid.
A stop on the Shinkansen is like a stop on a metro. The train stops, the doors open, people get on and off for a minute or so and then the train pulls out and immediately accelerates to cruising speed.
A stop on the TGV always takes at least 10 or 15 minutes, and the train does not get up to speed for another 10 or 15 minutes after that.