30+ Behaviors That Are Only Acceptable in the U.S. According to Non-Americans

Using “Sir” to address men in a respectful way is common across the world—whether it’s to address professors, military officers, cops, teachers, and more. It’s also often used as a polite way for retail workers to address customers, and as a way to get the attention of someone who’s name you don’t know, as in the phrase “Sir, I think you dropped this.”

So, for this person to be baffled by it, I guess they either live in a country where this isn’t at all common, or they just don’t address people respectfully. Maybe we Americans just have better manners than wherever this person is from. Don’t look at me that way – it’s possible.