Do they not have passenger assistance schemes in the US? Most major transport providers in the UK have them, though in practice they can be hit and miss – I've had a lot of excellent experiences and a few not-so-good (but not disastrous) ones.
Airlines tend to be the most problematic, but that's largely because wheelchairs have to be carried in the hold, and can come out damaged due to being mishandled.
Railway schemes are generally pretty good nowadays. The type of assistance provided varies according to the needs of the passenger – for instance, if you use a wheelchair, they'll ramp you onto the train (and demand the removal of all the luggage dumped in the wheelchair space by selfish idiots!). If you don't have a wheelchair but struggle to walk across the concourse, they'll take you to your platform on an electric buggy and help you find a seat.
You can book assistance for your whole journey, so they get you onto the train at the beginning, and then meet you when you disembark to change to another line to help you onto the second train. At the end of the journey, they can help you get to the taxi rank or bus interchange.
It's well worth researching what help is available, and people's experiences of it on the various carriers.
ETA: in the UK, there's also the Sunflower Lanyard scheme, which advises transport companies, supermarkets, etc that the person wearing it has a hidden disability and might need extra help. The disability could be anything from bowel problems to autism to heart disease, so it's not specific – but staff know they should give you priority, and possibly offer you things that aren't generally available (such as using the staff toilet if you have IBD).