Well, first of all, I'd like to thank Mr. Mephisto for his compliment, unless it's some backhanded compliment thing, in which case, I withdraw my thanks
Having said that, I'd vote for either George Marshalls address explaining the Markshall Plan, Kennedy's address to the public about the Cuban Missle crisis, Kennedy's inagural address in 64, or, if there's time, the checkers speech by Nixon. The Marshall plan speech is pretty obscure, so you shouldn't have to worry about anyone else doing it. Unfortunatly, it lacks the general passon of other speeches, so you may loose points on that. The Missle crisis speech might have other takers, but it's a good one about the US defining the Soviet union not just as the Russians, but acknowledging their attempts to influence the world, which later led to the "Domino Theory" that got the US into Korea and Vietnam. Finally, the Checkers speech is probably too long (it runs about 30 minutes total, but you might ask if you can do just the end), but it's one of the MOST blatantly self-serving political manuvers in the history of modern US politics, which IMHO, makes it worth a look.