vs.

https://commons.wikimedia.org/wiki/File:California_populatio...

The reddest areas on the California map would be orange on the Taiwan map.

A San Jose to Bakersfield route (comparable in length to the Taiwan route) has a huge low-population density area around the middle, so basically there's no prospect of using the rail for shorter trips. And the number of daily trips between San Jose and Bakersfield is likely to be limited.