Be sure to look at the beautiful view of Harpers Ferry when it pulls into the station. It's a lovely town built on a hill and has a lot of history. It's probably my favorite place along the Capitol's route.
You'll also get a look at Lake Erie between Cleveland and Toledo. The last two hours of your trip will give you a great view of steel mills and some of the industrial areas near Chicago.
Tracy is on train 30, which is traveling eastbound from Chicago to Washington, D.C.
Tracy, welcome to the United States, and I hope you will enjoy Amtrak. It will be quite different from British Rail. The Capitol Limited operates with double deck Superliner equipment. I don't know how to do links, but somebody else on here will probably be able to do so when they see my post.
Your room is well located. It is on the top level near the center of the car, and the stairs to the lower level. There is a bathroom (wc) on the top level, and several more on the lower level. There is also a shower on the lower level. There are shelves for you to stow your bags on the lower level. There will not be much room for luggage in your room so plan accordingly. The room will have two facing seats, and the top bunk may seem somewhat claustrophobic. Only the person in the bottom bunk can look out the window. There are rooms on both sides of the aisle, and the car can operate in either direction, so it is impossible to tell which side your room will be on.,
The dining car should be an enjoyable experience for you. Dinner, Breakfast, and lunch are included in your sleeping car fare. After the unreliable catering on British rail, you will enjoy the sit down meals. Amtrak's website www.amtrak.com will provide you links to sample menus. Also, I believe by the time you travel, there will also be a lounge car where you can buy alcoholic beverages, snacks, etc.
I don't know what time of year you will be traveling. In the summer you have longer daylight hours, and should easily be able to see some of the sights leaving Chicago. About 20 minutes after leaving Chicago, the train makes a turn to the left and angles across the Dan Ryan Expressway. If you are on the left side of the train, you can see a nice view of the Chicago Sky line. About 10 minutes later you will get your first view of the steel mills and Lake Michigan. If you happen to be awake about 20 minutes before Sandusky, You can see the crossing of Sandusky Bay. Even though it is night time, with the lights turn off in your room, you will be able to see quite well.
Downtown Cleveland will be on your right as you pass through Cleveland, and the Rock and Roll hall of Fame will be on your left shortly after pulling out of the station. You will see the Cleveland Browns stadium on your left shortly before arrival into Cleveland.
About 30 minutes before Pittsburgh, the train starts running along the Ohio river which will be on your right. Even thought it is night time, if you happen to be awake, this is a nice view. After Pittsburgh, you will have lots of views of the Allegheny mountains as the train makes its way to the summit at Sand Patch which is about 30 miles from Cumberland Maryland. You will have a since of the train climbing to the summit, and descending into Cumberland. After Cumberland, you will enjoy the ride along the Cumberland River which is mostly on the left. There is one place where the train passes through a tunnel, exits the tunnel onto a bridge over the river, and then enters another tunnel. This is about 40 minutes beyond Cumberland IIRC.
Some other things to remember. The trains in the U.S. share tracks with freight trains, and are sometimes delayed by them. The freights also wear down the track, which makes for a bumpier ride than you are used to in England. Most of the line is double track, so you will see lots of freight trains. At times, your train may switch tracks to overtake a freight traveling the same direction. This happens frequently between Chicago and Cleveland.
I hope you have a great trip. I visited the UK several times, and have had wonderful experiences each time. I enjoy the vastness and variety of your rail system. The roomette will be smaller than rooms on the overnight sleepers in operation between London and Scotland. However, the food service in the dining car will be better than on these trains. Good luck