Done to Americans? Crime worthy of death!
Done to suspected terrorists? Oh, no biggy.
Congrats! You finally get it!
Seriously though, we waterboard our own troops in SERE training. The war-crimes executions were never exclusively about waterboarding either, that was just one item on a long laundry list.
Yes, it is perfectly ok for us to waterboard non-American unlawful combatants if we have reasonable evidence they pose a threat to us and won't give up the info. Waterboarding is rough, but calling it "torture" puts it on the level of hot irons and racks, and it isn't.
But even more importantly, I don't accept that we have to give them moral equivalency and say "if it's wrong for them to do it, it is wrong for us to do it."
Why? Because there is no moral equivalency between America and Al-Queda. Our end purposes are very different, our modes of operation are very different: they saw the heads off of civilian journalists. THAT is torture.
Even if there were some moral equivalency, I wouldn't care, because we're us and they are "them" and we're at war with each other.
We should never let Amnesty International or any other international "authority" try any American President for anything, nor even any American soldier. To do so is a surrender of our sovereignty. (That's what happens to you when you LOSE the war, btw.)
As long as we have the power, we make the rules. When we no longer have the power or the will to do so, someone else will make the rules and we'll have to suck it up and deal with it. That's reality.
On the whole, I'd say we exercise our power with far greater restraint than many historical empires have: Persia, Rome, the Caliphate, colonial Spain. Only the colonial British Empire held power with anything like the restraint which we employ.
If Al-Q and company succeeded in restoring the Caliphate and achieving global dominance for their extreme version of Islam, you can rest assured they would not be so gentle and reasonable.