Look, there's no denying that there's a lot of room for criticizing American foreign policy, especially its military interventions over the years. I think it's even reasonable to say that the majority of them have been ill-conceived. But it;s not accurate to say that ALL of them are and if there's a post World War II war that is justified it's the war in Afghanistan. People opposing THAT war frankly sound daft to most people. Like the Congresswoman who voted against entering World War II (the sole vote -- she also voted against WWI, but wasn't alone that time), facing such people you have to say under what conditions would you support fighting? Waiting until the Nazis/Japanese/Taliban/Al-Qaeda are attacking your neighborhood a little too late, no?
Nice discussion here: http://www.dailykos.com/storyonly/2009/2/17/194929/728/995/698695
Barack Obama said from Day One he wasn't against all wars, just dumb ones. In that sentiment he probably captured the common sensical approach of most Americans. When you are attacked there's really no other reasonable response. The only people who don't fight back are those too weak to do so, and there's not a very happy record for weak people in our human history. Weak political units can only survive if protected by some powerful entity (power being an extremely relative term in this context -- but relative power is the only relevant context for military conflicts).
Let's be very, very, clear on this. While Obama's opposition to the war in Iraq (the dumb war) was important to his winning the presidency, his support for waging justified war in Afghanistan was vital for winning the presidency. The voters would never have voted for a pacifist for commander in chief.