We *have* prototypical Americans?
Though I agree, if we were to imagine ourselves at our best, Jimmy Stewart might be a place to start. The question is, how much do we confuse actors with the characters they play?
Elwood P. Dowd, the friend of the giant rabbit (a pooka) in Harvey, is one of the kindest, most courteous, most optimistic characters in film. He's part of what I wish we were, as well.
How about Roger Thornhill, the reluctant hero in North by Northwest? How about Bunny Watson, the shrewd librarian in Desk Set? How about Atticus Finch, the courtly lawyer in To Kill a Mockingbird? How about Hildy Johnson, the feisty reporter in His Girl Friday?
How about none of those movies was produced after 1962? Jeez...