People easily tolerate 3h on a plane, and trains are much more comfortable than planes (more space, free to roam).
I trained around the eastern US a bit, and while north of DC the trains are heavily-used and a 'normal' experience, south of DC the trains were very laid back and comfortable. They're subsidised, so the tickets are dirt-cheap, few people use them, they're comfortable and spacious, have power for laptops, and even have an entire car dedicated to sitting in a lounge chair facing outward to watch the scenery roll by ("oh, more kudzu..."). The only downside is that the stations were only at major locations, so not many stopping points, which was fine for what I was doing.
I trained around the eastern US a bit, and while north of DC the trains are heavily-used and a 'normal' experience, south of DC the trains were very laid back and comfortable. They're subsidised, so the tickets are dirt-cheap, few people use them, they're comfortable and spacious, have power for laptops, and even have an entire car dedicated to sitting in a lounge chair facing outward to watch the scenery roll by ("oh, more kudzu..."). The only downside is that the stations were only at major locations, so not many stopping points, which was fine for what I was doing.