One of the things that has consistently mystified me about Americans' complacency with drone warfare is the underlying assumption that our current monopoly on drones is going to last forever. If it's ok for the U.S. to use drones to assassinate "terrorist" anti-American agitators in Yemen, what are we going to say when China starts using drones to assassinate "terrorist" Chinese dissidents on American soil, or Europe, or elsewhere? For all intents and purposes, we're already using killbots, and the really important point here is that airborne killbots can be used (for now) with impunity across borders.
"American Exceptionalism" basically means we allow ourselves to commit war crimes with impunity.
What is there to be mystified about? If any other state actor with drone technology does anything like what you are suggesting, they will cease to exist as a state, period. They know what would happen. The Romans used salt to make sure Carthago delenda est; America will use Strontium 90. America's social order may be iffy, but their ability to come together and destroy other nations when provoked is a matter of historical record. They have more than enough nukes left in their arsenal to pave any ten countries if provoked, and I am pretty certain random drone strikes killing Americans in Des Moines would be provocation enough. You are right about American exceptionalism, in the sense that "He who has the ability to destroy the planet, controls the planet." And before you point out that lots of nations have nukes, ask yourself this one question: In the seven decades since our species developed nuclear weapons, what was the nationality of the only human in history to use a nuclear weapon in anger? Here's a hint: He actually did it twice.