I'll add to Maxx a bit. Here's the deal. There're starting to be a few disabled restrooms with changing tables in them, sized for adults, and older kids, with, say it with me, disabilities. They're newer for us than in the UK, but it's a start.
I'm in a wheelchair, and my life is occasionally punctuated with bladder and bowel blunders, but, more often than not, I make it to an accessible toilet. I can, if given a reachable rail. God forbid a catastrophic public bowel blunder, though, because, I'd probably be in the same position as my sister, and, shortly after that, they'd be cleaning me off the walls, if no one stopped me, followed by my memorial service.
My sister is double IC, in a wheelchair, and cannot change herself, rail, or not. She's who they're intended for, so Mom doesn't have to rip her back apart, negotiating a filthy public bathroom floor, with an adult daughter, almost as big as she is. IC is a disability, in America, so, there you go. They're in disabled restrooms. If you're not, don't.