X-Men: First Class re-imagined the Cuban Missile Crisis as a conflict manipulated by mutants. In the sequel, X-Men: Days of Future Past we can now expect Richard Nixon and Vietnam.
Director Bryan Singer—who has been tweeting photos from set—gave his followers a look at a "pivotal meeting" featuring, as Entertainment Weekly points out, Richard Nixon, and a look at "Vietnam."
A casting call sheet for the film indicated that a large part of the film takes place in 1973, and we're aware there's some element of time travel given the fact that practically everyone who has ever been in an X-Men movie is in this film. (McAvoy! Stewart!) Given that time period perhaps the X-Men had something to do with us getting out of Vietnam.