I’ve got a lock on this,don’t worry.
First thing we do is build a time machine and go back and tell ourselves not to condone torture and degradation at Abu Ghraib and Guantanamo, but to treat our prisoners humanely according to the Geneva convention, the Bible, and our own Constitution instead of stripping them naked, smearing their bodies with feces, threatening them with dogs, wiring their genitals with electrodes, and taking pictures of them with our smirking soldiers and thus giving ISIS the most perfect anti-Christian/West/America recruiting tool it could hope to have.
Then we could take the time machine and go back to 9/12 and tell ourselves not to treat a bunch of loosely affiliated thugs as the second comings of Nazism and the Iron Curtain, but rather consider them to be just what they are: Criminals who need to be tracked down, arrested, brought to trial, convicted, and imprisoned instead of being elevated to the status of a nation-state by declaring war on them.
In fact, we ought to take the time machine back to when we were supplying them in the mountains of Afghanistan because we wanted to give payback to the Rooskis for helping the North Vietnamese, and instead get our spies and arms dealers to stop doing that.
While we’re at it, we can go back to the day after the fall of Dien Bein Phu and instead of being all pissy and splitting their country in middle and importing outsiders to run our half, we can be good sports and shake Ho Chi Minh’s hand and congratulate him on winning independence for the united nation of Vietnam.
No, wait! Better still, we can go back to that moment when we broke our promise to Uncle Ho, who after fighting by our side against the Japanese in WWII was rewarded with betrayal and treachery when we handed French Indo-China -- ‘scuse me, Vietnam -- back to Charles DeGaulle, and instead tell ol’ Chuck to go oui-oui up a rope; America honors her promises.
Of course, it wouldn’t hurt to go back to 1918 and not invade Russia in order to support counter-revolutionaries in their civil war; after all, Europe sat back and let us duke it out during our civil war, so maybe we would have been better off saying, “Not our circus, not our monkeys” and just letting them hash it out amongst themselves instead of throwing our lot in with the losers and souring relations with the winners.
And maybe getting involved in WWI wasn’t such a hot idea, either; Germany and the Austro-Hungarian Empire were already collapsing before we joined in. Yes, we sped things up, but maybe if we hadn’t thrown our weight behind England and France they wouldn’t have been so draconian in negotiating peace, maybe even allowing the Kaiser to stay on the throne and keep Germany stable the way the Emperor kept Japan stable after WWII and then maybe a certain corporal would have ended up going to art school after all.