... which cast Bush and Cheney as the baddies (incompetent and villanous, respectively). We ended up shelving it because 9/11 kind of threw things into disorder (and subsequent events were too sad to be funny!). But I think you're definitely onto something -- some (if not all) of the British pantomime might translate quite well. (There have been numerous successful productions in Canada, which in terms of pop culture is more like the US than England.)
The younger kids would like the audience interactions and slapstick, and the older kids and grownups would like the social and political comments. Funny you mentioned Johnny Appleseed, because that's the first one that popped into my mind (and environmental themes are hot these days!).
Real historical characters -- Paul Revere? A funny look at the background leading up to the historic ride? Paul's still the hero, but has a bumbling comic sidekick, and of course a snobby aristocratic villain. (I think a couple of children's books have already had a go at the situation.)
How about regional interest? Where you are might help suggest some possibilities. TechBear mentioned Native American legends. This website lists characters I'd never heard of (like Alfred Bulltop Stormalong, on the East Coast). And Davy Crockett's girlfriend, Sally Ann Thunder Ann Whirlwind.
http://www.americanfolklore.net/ff.html