yeah, geography is an issue, the big cities in the US is usually a lot more spaced out which makes high speed train somewhat less attractive. In Taiwan the main issue is everything between the 2 major city is pretty highly populated too so there's a lot of major stops in between, the fastest normal train between the 2 city takes a bit more than 4 hours because of that, where as the high speed train is at most 2 hour (the once with only 1 stop will be there in 1:30)
price of tickets for the 4 hour trip is about 28 bucks USD, high speed train is about 47.
plane ticket is about 70 bucks, flight itself is 40 min but once accounting for the wait time (there's usually only 3 flights a day there, the high speed train units at least 3 an hour and usually more like 6) . and the distances of airport, it is likely to take LONGER to fly for nearly twice the money. so it's no wonder that passenger flight between the two went from 1.3 million passenger before the highspeed opened to ....25k this year before the last passanger company decided to stop that route (from as much as 7 company at it's height).