Oh yeah, come to papa. I'll try to list chronologically.

Maybe the first "American" painter that became well know was Benjamin West, who painted pre-revolution and later post revolution.

American portraitist Gilbert Stuart worked during the American Revolution and after and painted famous Americans.

You may have heard of Emanuel Leutze who painted this famous American icon.

Martin Heade was another prominent landscape painter, who also painted flowers.

Samuel Morse, famous for Morse Code, was also a painter.

The list goes on and on and on, and there are too many for me to put here, so I will skip on to some more interesting modern painters.

The Depression and the 30s were characterized by the Farm Securities Administration which sponsored American Documentary Photography with prominent names such as Walker Evans and Dorthea Lange (not painters, but very historically important for documenting American life).

Norman Rockwell is another artist with a long and prolific career who painted scenes from American culture.

Along with the above, Edward Hopper is another famous American who painted this famous painting.

The inventor of Pop Art, Andy Warhol became famous in the 60s and portrayed contemporary America.

Edit. If you want, I can give you more specific answers for any decade after 1900, but there's really too much to go through in this broad topic. For some great reading I recommend two books: Art Since 1900, and Art in Theory 1900 - 2000. I am not that familiar with pre-modern art, though I can help with a general outline.

There's a whole category of 19th century genre painters who focused on day-to-day life; you might want to look for paintings by George Caleb Bingham like Fur Traders Descending the Missouri , Richard Caton Woodville, and William Sidney Mount, as well as early work by Winslow Homer for 19th century genre painting. Moving to the turn of the century, the Ashcan School was enormously influential in shaping how the modern american city would be depicted; I would look at paintings by George Bellows, Robert Henri, and John Sloan. Is there a particular research project you're interested in or are you simply looking at paintings for pleasure? If the latter is the case, you may want to look at the catalog for the recent-ish Metropolitan Museum of Art exhibition "American Stories: Paintings of Everyday Life 1765-1915".

Are you looking for American themed artworks, illustrating America? Or are you looking for artwork that is representative of American ideals?

/u/TheSSir did an excellent job covering the most famous ones (Edward Hopper being a personal favorite), but I figured I would add a few others I loved from art classes. Since my knowledge is mostly of modern art all the artists I list will be from around 1880 - 1950

Winslow Homer has some excellent scenes of American life, particularly of ocean scenes and New England.

John Singer Sargent, although American themed art and landscapes were certainly not his focus, he was a very famous artist from the States who has some excellent select pieces of American life.

George Bellows was best known for his night scenes and dark pallet, particularly in Steaming Streets.

Andrew Wyeth created this famous painting while in Maine. This one happens to be another personal favorite.

Georgia O'Keeffe didn't paint "everyday" life, but drew her inspirations heavily from the American West. Most of her well known works are based off the flora and visual aspects of the American deserts.

I know you specifically wanted paintings but I feel you may be missing out on some amazing artists if you omit the field of photography. My study of focus has mostly been on painters and photographers from 1850 - 1950. Early photography relied heavily on the elements of painting since it was kind-of-sort-of a similar format. Early photographers who focused on American life would include:

Timothy O'Sullivan was commissioned by the government to photograph the American West.

Ansel Adams is perhaps the most famous American photographer. He photographed American landscapes almost exclusively.

Lewis Hine was famous for his photographs of common laborers and child workers in America.

These are just a few of my favorites. If you have any questions or wish to see more I'd love to share more of what I know.