This comment explains it pretty well:
Well, as long as you're being specific...
That comment says nothing new. It repeats the same stuff you've already said across this thread, and provides no evidence to back up the assertions. It does get the basic facts wrong, though: the vast majority of traffic on the "Tokyo to Kyoto" line goes between Tokyo and Osaka. Those cities are big (~9 million people each; Nagoya and Kyoto are comparatively small at ~2 million people each), but they're still only ~14% of Japan's population (17% if you include Kyoto and Nagoya).
Again: the only thing that matters is the number of people traveling between the points on the line. We know these things, and it's clear where high-speed rail would work. We don't need to have nebulous debates about "economic value". And arguing that "people don't buy Eurail passes" is absurd on its face. They certainly would, if Eurail actually existed.
You keep repeating this "top ten cities" thing, as if it's important. But the only question that matters is: do enough people/things travel between X and Y to justify investment in a rail system at cost $Z? That's an actual debate we can have. Moreover, regardless of what you think of Seattle and Portland, if you don't count SF and Los Angeles (again, 380 miles) as important American cities, I don't know what to say to you.
"The people of Houston, Atlanta, Miami, and Phoenix hardly benefit at all from coastal HSR --- which is already happening anyways."
Atlanta to Miami: 662 miles. Houston to Dallas: 239 miles. Dallas to Denver: 800 miles. There are many, many regional connections in the US that make economic sense for HSR. Not just coastal lines.
But no, it's not already happening. We have a few projects that look increasingly likely to die. Because literally every time the subject comes up, naysayers are there to argue that the USA is just fundamentally exceptional to every similar place where HSR is working well.