Okay, here is some more information on the benefits of high-speed rail (HSR):
The optimal distance is 100 to 400 miles (or a 2- to 3-hour journey); generally, journeys of up to 400 miles benefit from not having to check-in, do security checks, suffer delays, claiming baggage, etc., as you would in airports. This is assuming, of course, things are running as they should with HSR. Apparently, the systems can be well run compared to the "typical" airliner.
Compared to automobiles, even the low end of the HSR travelling at 125 mph is substantially faster.
Spain has an HSR network of nearly 750 miles, while China has over 3,700 miles.
(
http://en.wikipedia.org/wiki/High-speed_rail)
That covers a lot of area. I know the U.S. is big, but when you plan it properly, you'd have webs of regional coverage linked up possibly with some express routes in between.
The bottom line is that there is a lot of potential for such a system both in the U.S. and Canada merely because of the distances required to travel. Travelling 400 miles is quite a distance without having to fly (and waste time getting on and off) or drive and still get there in under 3 hours. That's like Los Angeles to Phoenix, or Toronto to New York City.