What is the percentage of restaurants that serve American food in Dublin city?
American food refers to food_type = 'american food'; percentage = divide(count(id_restaurant), count(id_restaurant where food_type = 'american food')) where city = 'dublin' * 100%
SELECT CAST(SUM(IIF(food_type = 'american food', 1, 0)) AS REAL) * 100 / COUNT(id_restaurant) FROM generalinfo WHERE city = 'dublin'