For me, it’s the American belief that their laws apply in other sovereign countries. Calling Julian Assange a traitor when he’s Australian and never held American citizenship for example. Demanding his extradition and strong-arming other countries when he’s not beholden to American laws nor constitution as a non-citizen, and believing that it’s their right to do so.
And that’s from speaking with countless American who believe that this is totally justified and above-board.