Id never order a tuna fish sandwich but I’d make them. I’m from pnw USA. When I say tuna sandwich I feel like it would be different than something out of a can. Tuna salad probably makes more sense but ive never had any confusion when saying tuna fish. Doing some googling, “tuna” is also Spanish for “prickly pear”. So tuna could be used to describe a cactus fruit. In Cali there is a restaurant called “La tuna canyon”. Not cause of the fish.

From merica, Pacific Northwest. My experience is hot you’ll get some hot water in a kettle with a box of various teas, or iced which is non sweetened, can add sugar if ya want. If I just said “tea”, they’d ask hot or iced. Id feel strange just saying “tea” without being more specific.