Earlier quoted context omitted.
Americans consider hamburgers to be a type of sandwich. It can be confusing to people from other countries who don't consider meat in a bun (as opposed to meat between slices of bread) to be a a sandwich.
Sorry to keep doing this, but I would say a bun is bread, too: “A bun is a small, sometimes sweet, bread or bread roll,” quoth Wikipedia.
I guess likewise, because while bun is a type of bread, bread doesn't, again, necessarily have to be a bun.