There is a tradition of anti-nobility sentiment in US culture as old as, well, the US. It is literally written into the Constitution[1]. How much you were exposed to it probably depends on where you grew up; I think it is louder in the north east, and I don't hear it much in California.

Personally, I am more annoyed at being sir-ed constantly. I much prefer to reserve it as a genuine term of respect, not a generic form of address.

[1] Article I, section 9.