Answer:
I am not sure if I understand your question.
Do you mean A) a world-famous painting which is in a US museum or collection?
Or do you mean B) a painting which is well known to US people?
Or perhaps C) a famous painting by a US artist?
In A) there could be an almost endless list. US collectors and museums own a great part of the most famous paintings in the world.
The Metropolitan Museum of New York owns the Wheat Field with Cypresses by van Gogh, and many well-known impressionist paintings.
The Museum of Modern art and the Guggenheim Museum in New york own many famous paintings, for instance The Red Studio by Matisse.
Seurat's Sunday Afternoon on La Grande Jatte is in the Art Institute of Chicago, etc etc.
The above answers question B) as well.
Under C) I could mention some of Andy Warhol's works: Campbell's Soup and Coca Cola Bottles, Jackson Pollock's Blue Poles and others. Georgia O'Keeffe's Ram's Head, Mary Cassatt's Mother and Child. And so on.