You can't really fight for freedom unless the force you're fighting against I trying to remove it. The Nazis and Japan weren't really in a position to remove Americas freedom. The merits of Korea, Vietnam, and the various Middle East invasions are really neither here nor there.
Those who sign up deserve a certain level of respect simply for putting themselves in harms way. They don't get to pick and choose where and whom they fight.
However this whole "They're fighting for your freedom" is jingoistic wank.