For really long construction work they’ll actually build an entirely separate train station, like they did in Denver Colorado a few years back. They knew that the construction of the new station downtown would take a few years, so they built a really cheap platform a few miles away on a siding and moved all the arrivals and departures there for the duration.
The Amtrak people I've met over the years pretty clearly want to do a good job in a system that is stacked against them.
https://media.amtrak.com/wp-content/uploads/2024/07/Autumn-1...
Up top are seats and maybe a lounge, below are bedrooms, bathrooms, and storage. There's a spiral staircase to change levels.
The locomotive has steps right outside the wheels with handrails.
It's pretty obvious where the doors are (middle), which have windows. My point, replying to my parent, was that they said Amtrak platforms are at 110cm height. The lowest part of those doors are not at 110cm height, but much lower, almost as if the platform was much much lower than my parent claimed ;)
And yes, trains do exist, which either have doors at two different heights (these don't seem to) or that either automatically fold away so you can get out at ground level via the stairs that are revealed/created by the mechanism or that simply stay up for platform height entry/exit. Used both types. Now, whether or not Amtrak has those in specific parts of the US I can't say.
Every car has a metal step that will be placed in front of the door by the attendant.
Edit: Oh, except for a few lines on the East Coast where the trains are only single–level. Those are 48” above the top of track.