The northeast and west coast metropolitan corridors are similar, and combined have comparable populations, densities, and distances as Japan. Yet we can't even build a single high-speed line. And for all the excuses about the difficulty of building rail through developed regions, the existing rights of ways and infrastructure in both the NE and California are comparable to what everybody else has had to work with, at least in the past 50 years. The density of the NE is nothing like what you see elsewhere in the world, especially Asia, and Japan and China specifically.
It's lack of political will and ambition, period, by both the community and leadership. And excusing our inability by pointing at the hurdles, insinuating that others succeeded because they didn't face the same challenges, only perpetuates the paralysis.