and of course I perplexed my US hostess when I asked if I could help lay the table.

Following on from wash up, there are differences on the room where one (or even more) excretes. The US usage of bathroom for this is only following a long tradition; lavatory, toilet, any others? But when asking for a "bathroom" in UK you would be shown a room that had a bath in it but not necessarily a toilet/lavatory.

Rod