When entering, "any allergens or intolerances" is normally asked before you're sat down. They distinguish the two to decide whether a station clean is required or if they can just point you to the menu.
If it's not already clear on the menu, most medium/large chains then hand you a tablet letting you filter by almost anything.
If you are working with food you should know about allergies. It just comes with the territory. I’m baffled by how this is somehow too hard for US folks yet we manage fine.
It's just yet another arena where the US likes to wring its hands and make excuses for why the US can't do what all manner of other countries manage to do without issue, from things like this to mass transit to Internet connectivity to gun control to ... we're just soooooo unique that solutions that work elsewhere couldn't possibly work here.