This is nonsense. Burgers are sold in damn near every country.
Except Americans will only call it a 'burger' if it's a beef patty and garnish on a burger bun. What we call a chicken burger, they call a chicken sandwich - which is ludicrous because a sandwich is something between two slices of bread, not two halves of a bun. Heck, the even call Subway's fare 'sandwiches'.