I know it probably depends on the movie, but is their a site somewhere that shows how much presidents make when they are in a film? I have seen several “interviews” of Bill Clinton in movies such as, The Siege. I assuming they paid him in some way or at least contributed to his party. Do they just call up the whitehouse and ask him if he wants to appear in a movie?
I’m not sure I remember Clinton in The Siege, but I assume they used some news footage that they got from a network, not from the president. I remember in Alien Nation they had a clip of Reagan making a speech and I’m sure they bought the rights from CNN or whoever. I’m not aware of a US president appearing in a movie (maybe a documentary). The movie Traffic had actual US senators appearing in a scene talking about drug policy at a cocktail party, but I remember reading that they did it for minimum scale and donated the money to charity.
IIRC the film Dave had a number of serving senators in it, but then, it was about an stand-in pretending to be the President.
I’ve never heard of a sitting President having an actual role in a non-documentary film. News footage is used all the time, of course, and occasionally they do neat tricks to make it look like they’re saying stuff relevant to the plot. (See Contact, for example.)
Congress-critters show up in background cameos all the time, though. One obnoxious Republican once criticized John McCain for appearing briefly in the somewhat raunchy Wedding Crashers. Sen. McCain replied, “I don’t mind appearing in a movie that showed boobs. I work with boobs every day.”