A political party by the name of the American Party has existed several times in the United States:

United States (essays) summary and related information.

There were also several other late 19th century nativist political parties with the same name, notably including one founded in 1887.

The antebellum American Party grew out of the Know Nothing movement and was based on nativism.

The American Party was a successor of the 1968 American Independent Party. The current American Independent Party split from it in 1976.