From what I have read traincrew jobs in the US are highly seniority based. You start off as permanently on call, where you are given as little as an hour’s notice to report for duty at any time of day or night and could spend days or weeks lodging away from home. As above, you must start as a trainee conductor and work your way up the ladder, eventually, to engineer. For the class one railroad companies the link structure works almost in the opposite way to the UK, in that the local yard shunting jobs (with fixed rosters and rest days) are reserved for the most senior men and the young pups are sent out in the long distance trains with no fixed schedule and having to lodge.
The working culture and approach to safety is completely different to ours and you would have to learn a whole new railway language and way of operating (for example, try googling to resd about some of their baffling - from a British perspect at least - signalling systems).
As mentioned above, to get a foot in the door to start with you would need a green card and no railroad company will sponsor you for that so you’d need to qualify in some other way or enter the lottery (UK residents are now eligible for this).
Here is a video describing work as a conductor (which is how you would start) -
This video refers to being on call at 90 minutes notice 24/7/365. I also found a document from the Association of American Railroads which states that the average number of annual leave days (called Paid Time Off, PTO, in America) per year for operating staff in the class one railroad companies is 15 days.
Here’s a Union Pacific video which explains on call, rest days, furlough and seniority -
Here’s another video picked at random where a BNSF conductor describes his job and the seniority system. There are loads of these on Youtube -
The interesting bit starts at 3 minutes 26 seconds