Tim:
If you haven't got there by now, here are a few quick handy conversions:
An inch is exactly 25.4 mm, by definition, which gives you right at 3.28 feet per meter. Yes, 2 meters is right at 6 feet, 6 inches. Don't attempt to decimalize feet. For the most part, use feet and inches. If exactly 2.000 meters, then call it 6 ft, 6 and 3/4 inches. Don't know where you are coming from, but the use of commas and periods in dividing numbers is exactly backwards between US and Continental Europe. In other words, if writing 24 thousand 350, in US style it would be 24,350, not 24.350 or 24 350. Likewise, the 25 and 4 tenths millimeters per inch is 25.4 American or 25,4 Continental.
Think of a mile as 1.6 kilometers and you will be very close. A kilogram is 2.2 pounds. Thus, if you weigh 100 kg, that would be 220 pounds. We have never used the British style "Stones" in calling weights.
Standard US electricity is 110 volts, 60 cycles, so any electronics you bring best have adapters for the current, or you will need to get them here. That may be hard to find. You may be more likely to find the things you need in this line before you leave whereever you are coming from.
You generally cannot sleep of the floor in coach. The seats will be larger than you have on most (all?) European trains. American coaches are somewhat wider.
American track will ride rougher than in Europe. For the most part the norm is that the railroad company, which is not Amtrak owns and maintains the track. Amtrak operates the passenger trains, but the tracks are owned by the railroad company that operates the freight trains. For most of the Empire Builder's route that means BNSF. For the Coast Starlight south of Portland Oregon that means Union Pacific. They are maintained for safety, usually to a better conditions than Federal track safety standards require, but for some parts of the route, not a lot better. The ride gets very rough before you approach the limits of safety. Relax, but remember to be ready to grab something when up and about.
Also, the passenger train loading on the track is far less than that of a US freight train. Am American Superliner car is 4.93 meters high and weighs around (in 1000 kilogram tonnes) 17 to 18 tonnes per axle, depending upon type and loading, the diesel on the front end each weigh in at about 30 tonnes per axle. A fully loaded freight car will weigh up to 32.4 tonnes per axle. Freight trains can be upwards of one mile long (that is 1.6 km) and weigh 10,000 tonnes in total. The top of the top container on a train of double stacks will be at 6.15 meters above the rail. The BNSF line across the the nothwest is a fairly busy piece of railroad, and for the most part single track.
On this line across the the northwest, you will go through the two longest railroad tunnels in the US, the Flathead Tunnel in Montana and the Cascade Tunnel in Washington. The Flathead Tunnel is 7.01 miles (11.28 km) long and the Cascade Tunnel is 7.79 miles (12.54 km long. No electrification. If you were to come back east on the California Zephyr, you would also get to experience the greatest change in elevation in one bite in North America, from just above sea level to over 7,000 feet (2150 meters).