The airline industry is dear to the hearts of congressmen, who fly back to their districts on the taxpayer dime, and subsidize the industry in all sorts of unique ways. The US Postal Service, for example, is compelled to subsidize air service in Alaska -- random towns of 250 people get 3 flights a day in many cases.
The rail business was put out of business by bitter labor disputes, subsidized highways and air travel in the 1960's. The direct Federal takeover of the industry (ie Amtrak) makes it difficult to function in a rational way, as it is subject to the whims of Congress. Amtrak is compelled, for example, to serve food on trains -- a service that loses millions of dollars annually.
High speed rail has a lot of land acquisition problems for the most part, air flight doesn't.
I say let the high speed rails come naturally (because they will eventually): don't try to force it.
High-speed rail in the Boston-DC corridor would be pretty pricey, too. Amtrak tries it, but their idea of "high speed" is sad compared to what the rest of the world thinks it means. While the Acela is somewhat similar to the TGV, it peaks at only 150MPH, and the average speed is far lower because the track doesn't support high speeds in a lot of places, and because it makes about three times more stops than it should.
Proper high-speed trains in that corridor would require new tracks built for much of it, and with level crossings pretty much impossible for high-speed trains, it would need a ton of bridges or tunnels and a huge expense. A lot of politicians will only support such a thing if they can bring service to their hometown, or where their constituents live, or whatever, so you end up spending way too much time stopped at irrelevant stations instead of going fast. The Acela makes seven stops between DC and New York alone, not even counting DC or New York themselves. It makes six more stops after NYC before getting to Boston. Covering a similar distance in a rational high speed system would involve maybe one intermediate stop. As it stands, when I take the train from DC to NYC, I don't even bother trying to get a place on the Acela unless it's the cheapest option, because it only saves about half an hour out of a four-hour journey.
I think it's ultimately a self-fulfilling prophesy. People don't think it can work, which allows politicians to screw it up, which means that it either never happens or happens poorly. So it doesn't work, and people don't think it can work, so....