The average America has little personal experience with corruption. I wouldn't dare even suggest to a cop that he take a bribe to make my speeding ticket go away, while in many other countries that sort of low-grade corruption is standard. I think this experience leads many Americans to falsely believe that America is generally free of corruption, which of course isn't true in the higher rungs of society. Rich people in America commonly bribe politicians, universities, etc. It's a whole different game for them, they play by a different set of rules that most Americans have never been exposed to.

(I think it works this way across the anglosphere, not just America. The average Briton can't bribe the average British cop, but their royals/etc certainly pay to make crimes go away.)