If the U.S. doesn't take this on, I hope another country with a big appetite for enormous public transit projects takes this on. Japan, Korea, and China, I'm looking at you...
The places where this would make sense have destinations fairly far apart, but not too far apart, with somewhat amenable landscape between them. The Midwest would work, Australia, Russia. Probably Brazil, Argentina? Probably a bunch of connections in Africa or maybe the Mideast... but that wouldn't work for other reasons. East coast seems a bit cramped.
The public in East Asian countries see public transit in a different light than most North Americans, partly due to a lack of cars and the population density. They are probably the some of the few governments that can afford to foot the bill for such an unproven project with potential for dramatic benefits (and cost savings over building HSR), but also with the risk that the 10 billion or so could go down the toilet. Europe would be another ideal target, but I doubt any governments there have the appetite for big capex infrastructure projects right now.
In Australia this could potentially be viable between Melbourne and Sydney, but probably only if it doubles as a cargo train. I doubt there is enough daily people traffic to warrant it otherwise?
It is around 900km though, almost a straight line along the Hume highway and the busiest city-pair in Australia by a long way.
>I doubt there is enough daily people traffic to warrant it otherwise?
Sydney<->Melbourne is the third busiest air route in the world with 8 million passengers in 2012[1]. I'm sure there's more than enough "potential" passengers.
