Which phrase compares something typically American to apple pie?

The phrase is “as American as apple pie.”

The expression compares something regarded as characteristically American with apple pie, a dessert that became a powerful symbol of American culture. It does not claim that apple pie originated in the United States: recipes and traditions for apple pie came from European sources, especially England, and were adapted in North America.

In the United States, apple pie became linked with prosperity, home cooking, national identity, and patriotic imagery during the 19th and 20th centuries. That cultural symbolism made the phrase useful as shorthand for something familiar, traditional, or recognizably American.

The wording is related to other patriotic associations, including “for Mom and apple pie” and the advertising-era pairing “baseball, hot dogs, apple pie and Chevrolet.” Those are neighboring expressions, not the answer to this question. “Baseball and apple pie” is a cultural pairing, while “as American as apple pie” is the established comparison idiom.