In a high-density environment (hey there Japan!) HSR makes tons of sense. In a much lower-density area, moving people isn't the biggest problem, it's moving stuff.
Next time you take a long-distance flight in the USA, look out the window and ponder how dang big AND EMPTY the country is. People can be transported quickly by air, but for cargo you want energy efficiency per kg (not speed). For most of the USA, it's completely rational to build a slow, efficient cargo rail network. The overhead of airports makes sense for human transport given the distances involved. This is different from Europe/Japan where the overhead of air travel matters proportionally more given the short distances between destinations.
It gets worse. The value of a (human) rail network grows as its density grows. Germany is awesome because the rail network connects a bunch of different cities. Even if the Seattle+Portland route makes sense in isolation, that's basically the entire network right there. Maybe add Vancouver? There's no other population center even close... just 3 cities in a line on the coast. There's absolutely no multiplier effect on the new HSR links. They'd be better served by building a small dedicated airport at either end and running frequent commuter planes back and forth all day.