320 kph is the maximum cruising speed. Average speed for a trip is typically much less than that because the trains can only hit 320 kph on certain stretches of track. Even 320 kph is about 30 kph short of what the California trains are planing to average. From what I understand the operating costs go up considerably between 320 kph and 350 kph due to the need for much more stringent track maintenance.
> 320 kph is the maximum cruising speed. Average speed for a trip is typically much less than that because the trains can only hit 320 kph on certain stretches of track.
France and Spain have those tracks in Europe.
The newer German tracks with 300km/h are operated at 300km/h with the ICE 3. Even through towns and tunnels. It's not the average speed, but a typical cruising speed on those tracks. France has more and longer high-speed tracks, thus the high-speed trains operate at higher average speed than in Germany.
Operating at 300km/h and beyond is indeed expensive. As are high-speed train in general. Still Western Europe now has an extensive amount of high-speed tracks:
Oh, most new track is designed for operation speeds far beyond what's commercially expected: it's very cheap to do (the primary requirement, after all, is about curve radius, which just affects your choice of route). The signalling, the overhead line equipment, the rolling-stock… all of that is all designed for the initial operational speed, because that does become expensive (or non-existent) if you want to push the speed up.
Germany uses 300km/h on some tracks. Here the view from a train at that speed overtaking cars on the Autobahn:
https://www.youtube.com/watch?v=Js3XDTE5Iyg
China learned from it, here using a version of a German Siemens ICE train, Shanghai/Beijing in under five hours. https://www.youtube.com/watch?v=xvytUaRs2dU