In what way is it fanciful? There's an extensive network of interstates in the US with nearly zero intersections. If it's viable for I-90 why isn't it viable for the equivalent rail line?
If you don’t mind losing I-90 for car use, you could just repurpose the right of way. Otherwise, you just need to build another I-90 for HSR, well, it wouldn’t need to be as wide, you probably could do more tunneling and viaducting through the mountains so it doesn’t slow down much like the real I-90 does. But in Seattle, I don’t think there is room for another new right of way, so you have to tunnel or somehow run it down the middle of the freeway (and forget about lake Washington, you would need a new floating bridge unless you could stomach the slowness of going around.
All can be solved with lots of money (and the space issues can be solved with even more money).
Well, if all the interstates did have plenty of intersections, and someone proposed removing them all retroactively, would that not be an absolutely gargantuan undertaking at present, to the point where justifying it would seem fanciful?
Given the current state of US passenger rail I suppose such a proposal is closer to building out the interstate system from scratch. Which is indeed a bit on the fanciful side.
On the other hand, who says you have to do the entire country at once? Perfect is the enemy of good and all that.
Japan has an average density of 338 people per sqkm.
There’s only 3 US states with a density higher than that (Massachusetts, Rhode Island, and New Jersey) and an additional 2 US states of at least 220 people per sqkm (Maryland and Connecticut).
The US isn’t population dense enough for such transportation to make sense.
Nobody’s proposing to build rail in flyover country, but there are many places where high speed rail make sense based on GDP and population density (CAHSR, DC-NYC-Boston maglev, DFW-Houston)
Flyover county was definitely included in my initial response about at grade crossings, but wasn't specific to passenger rail, and why wouldn't it hypothetically be included? There already is rail everywhere, that's why I suggested it's a bit fanciful, it's just mostly freight. Doesn't necessarily need to be bullet trains, but given how bad North America seems to be at building any major rail projects in the modern era, I don't really have high hopes for advancement in this area, just dreams.
I do tend to prefer rail whenever viable, and the cascades route is already halfway decent, just not competitive on any front except ease of access with flying.
Density over some wide area is the wrong metric here. An entire state is absurdly large (in most cases). Two dense endpoints can be separated by quite a distance and still be worth connecting.
All can be solved with lots of money (and the space issues can be solved with even more money).