Why not?
There's tons of routes in the US that could make sense if there wasn't so much NIMBYism, corruption and the oil and auto lobby, let's be honest.
SF-Sacramento, SF-LA, LA-San Diego, LA-Vegas, Seattle-Portland, the whole Northeast Corridor (a better truly high speed Acela), Houston-Dallas, Orlando-Miami, Pittsburg-DC and and and. There's lots of large cities in the US in the high speed rail sweetspot of 400-800 miles (2-4h travel time) apart