Bread is a requirement for something to be a sandwich, so you’ll have to convince me that a tortilla is bread. You might be able to make a case for the soft flour tortilla, but I just don’t see how hard corn tortillas can possibly fit under the umbrella of “bread”.
Are waffles bread? Doughnuts? Deepfry batter? Ricecakes? Mushrooms? Potatoes? Peppers, tomatoes, cucumbers, eggplants, apples? Cabbage? Egg? Cheese?
I’ve seen all of these used to make what can only be called sandwiches. Bread is certainly popular for it’s dry and durable structure, but it’s not a requirement.