Would a train trip be romantic?
When I was 26, I took a solo train trip across the U.S. I had a blast. I did not feel out of place at all. Just note that if you stay in a sleeping car, you cannot go sit with the others in coach. You can go to the observation car and the dining car. They sometimes show movies at night in the observation car. You should make reservations for dinner if you plan to dine in the dining car or you can eat at you seat or in your sleeping quarters. I stayed in coach the entire time. Even from D.C to Seattle. 3 days! It wasn’t bad, but I had a sleeping bag, a pillow, 2 blow-up pillows, ear plugs and a sleeping mask. The seats recline some and there is a leg rest. I made quick friends on the second day with someone who was in a sleeping car and used their shower.
Three things: 1. ViaRail over Amtrak any day. 2. I think you’ll only be as out of place as you let yourself be. What a great opportunity to talk with people outside your won age group. 3. It’s true that the demographic is more likely to skew older for the full coast to coast journey, but most of these trains stop all along the way, and a lot of the passengers will be coming along for shorter hops, and be of all different ages and backgrounds. Overall, the train population is probably more diverse than you think. Have a lovely time!