That is interesting actually. You could argue that the tiny amount of leave Americans typically receive contributes to emissions. With people being unable to spare additional time for travel there is a strong disincentive to use any form of transport apart from flying.

However, one could also argue that the majority of the nation does not have the luxury to spend a single day traveling, so going by sleeper train is even better. I recently had a business trip to Switzerland and took the sleeper train from Berlin to Basel (9pm to 8am) where I arrived after a nice breakfast (in the train) so much more relaxed than after a hectic flight. Its more expensive but only because its basically hotel + trip.

If we don't solve this problem you won't have the luxury of travelling anywhere, we will be spending all our energy and capital just on surviving.

Maybe not the majority, but certainly many millions of people in all kinds of jobs could conceivably work remotely for a day or two while traveling by train and lose less productive time than they would by taking a plane.

Also, if we really had bullet trains that could do 200+ MPH, you could have cross-country express trains that take less than 24 hours, so it wouldn't even have to be multiple days.