Some dishes that are typically considered American have their origins in other countries. American cooks and chefs have substantially altered these dishes over the years, to the degree that the dishes now enjoyed around the world are considered to be American. Hot dogs and hamburgers are both based on traditional German dishes, but in their modern popular form they can be reasonably considered American dishes.
Pizza is based on the traditional Italian dish, brought by Italian immigrants to the United States, but varies highly in style based on the region of development since its arrival. For example, "Chicago" style has focus on a thicker, taller crust, whereas a "New York Slice" is known to have a much thinner crust which can be folded. These different types of pizza can be advertised throughout the country and are generally recognizable and well-known, with some restaurants going so far as to import New York City tap water from a thousand or more miles away to recreate the signature style in other regions.