I certainly believe that bullet trains are a possibility in the United States.
Between cities like Dallas/Houston/Austin/San Antonio, Chicago/Minneapolis/St. Louis/Detroit and many other, I think they would be good, fast alternatives to airlines.
The only problem is that airlines have a strong lobby power, and I am pretty sure they would fight any idea of more bullet trains (or their existance period.) I seem to recall that Southwest vigourously fought bullet trains in Texas, but don't quote me on that.
Airspace is limited, and I think that a national network of rails is in order. I also think that all US airports should have passenger and commercial rail links, to fully integrate the two means of interstate transportation and commerce.
I don't think that a bullet train between say, San Francisco and New York is going to happen anytime soon, but I think that regional rail has a bright future. The public likes rail systems, as demonstrated by light rail success in many urban areas (even 'car happy' areas such as Dallas, Houston, and San Francisco.) The more rail the better. I think Americans just need more options than cars and planes, and the rail is a perfect intermediary.
None of this will happen, though, while we have a conservative, car clinging government. There will always be more money for crowded highways than railways.
"[He] knew everything about literature, except how to enjoy it." - Yossarian, Catch 22