The movement they started is called Pop Art. Lichtenstein similarly called the role of the artist into question with his gigantic, almost abstracted copies of popular comic strips. Both artists challenged traditional conceptions of art as well as cultural values, raising interesting questions about what really has value in modern society. As you can see, artists in the 20 th century deviated vastly from traditional art forms, challenging assumptions and generally wreaking havoc on American cultural sensibilities. And that's just painting.
Contemporary artists continue to do the same, perhaps even more so.