Population density of entire states/provinces is completely irrelevant. I trust you're aware that ~ 2/3rds of BC's population, for example, lives in a tiny strip of land (Lower Mainland).
There are 10 million people in Portland, Seattle and Vancouver metro areas, and the distance between the three is about 500 km. That would be more than enough density for high speed train in any part of the world. Spain's major population centres are a lot more geographically spread out.
I'm not sure I'd start with high speed rail in this corridor. The focus should be on high-frequency, high-reliability fast trains that may not hit the true HSR speeds, but at e.g. 200 kmh would be plenty fast enough for now. But the argument that "the population density isn't there" for HSR is absurd.
There are 10 million people in Portland, Seattle and Vancouver metro areas, and the distance between the three is about 500 km. That would be more than enough density for high speed train in any part of the world. Spain's major population centres are a lot more geographically spread out.
I'm not sure I'd start with high speed rail in this corridor. The focus should be on high-frequency, high-reliability fast trains that may not hit the true HSR speeds, but at e.g. 200 kmh would be plenty fast enough for now. But the argument that "the population density isn't there" for HSR is absurd.