Rail travel is an excellent alternative to air or auto travel and could be a memorable experience. It allows more room for you to get up and walk a must when travelling long distances. Unlike auto and air travel you are not trapped to a seat which is an added benefit which promotes mental relaxation. It allows you to observe and enjoy the nature that surrounds you.
Most countries including Japan and many European countries have high speed trains. They are a much faster way to travel in comfort compared to air travel. High speed trains travel over 200 miles per hour and equipped with Wi-Fi, café cars including fine dining and sleeping. European countries are expanding train travel from Paris to Barcelona, a 500-mile distance.
Many train travels especially in Europe, you can buy a train pass (Eurail Pass) before you leave the country that is valid for many days allowing you to stop and enjoy many places and cities. This is a hassle free advantage over air travel.
Amtrak is an excellent option in the U.S. It allows you to travel between east and west which takes you through many scenic places. Try Coast Starlight in the west coast and Down-easter in the east.