That's because they mostly avoided mountains on their high speed routes. The Tokaido and Sanyo Shinkansen mostly follow the coastline and the Tohoku Shinkansen mostly goes through a valley. There are lines that do bore through mountain ranges, but nothing to the extent of several hundred miles as would be required for a line through the California coastal range.
I feel like this sort of thing just proves that the problem with building high speed rail in the US is cultural[1] and political[2] not technical or economic.
[1] Americans have been carefully propagandized to believe that governments can't do anything right. And cars represent manhood and freedom.
[2] For instance Ubber and Lift are funding the same anti public transportation organizations the Koch brother(s) were.
Americans have been carefully propagandized to believe that governments can't do anything right
Then the people decide to give the government a chance, pass a proposition asking for rail, and then the government completely screws it up. Terrible route, corrupt, massively over budget, graft, and effectively cancelled after a decade of waste and work. So now even progressive people in progressive California are thinking the government can't so anything right, not because of propaganda, but because they see the failure.
And the current estimated cost of that hsr system exceeds the estimated cost of the entire 520 mi (840 km) phase 1 system in California. Imagine scaling the cost of a similar design to travel the distance from SF to LA, ignoring the fact that the Japanese tend to build these grand infrastructure projects far more cost effectively than we do.
Well, then definitely try the Kurobe Gorge mountain railway! It's a originally industrial railway in a deep valley that was used for dam construction. On the hour long journey it goes through none less than 42 tunnels & the view (when not underground :) ) is breathtaking. :)
