To elaborate on my earlier Amtrak post, I doubt that long-distance rail will be viable in America outside the Northeast corridor and perhaps a few other niche routes (Los Angeles to San Diego, etc.) anytime soon. This is for one simple reason: the US is too spread out!
As part of a small experiment, I decided to examine different modes of travel between Paris and Berlin. By European standards, these cities are some distance apart, but as the crow flies, they're only 545 miles from each other. This is roughly the same as the distance between Portland and San Francisco (535 miles).
I looked at prices for a round-trip ticket on a random pair of dates, August 1st to August 10th. The lowest air price was a stellar $151 on Lufthansa, while the lowest rail price was $304 -- twice as much! Not to mention, of course, that the rail journey takes 12 hours, while the air trip is a bit more than an hour and a half. Or that the lower rail price is only available on annoying, overnight trips (9 PM to 9 AM), while the air ticket has standard departure times of 9:20 AM and 5:20 PM.
Admittedly, entering in a few other dates suggests that the $151 I found on my first attempt isn't too common. The lowest fares generally range from $200 to $300. But for any sane person to choose rail over air travel on such a long trip, the train will have to display a genuine cost advantage. The fact that this advantage doesn't exist in an environment with vastly more developed passenger rail systems, on a trip that isn't at all long by American standards, suggests that we shouldn't expect rail to become a serious player in most long-distance transportation.
Of course, you don't have to take my word for it: just ax the absurd subsidies given to Amtrak, which are roughly 150 times greater per passenger-mile than those offered to highway transportation, and see what the market says...