If it bothered me I wouldn't have responded the first time. :)

I'm hampered because people I usually help speak mexican spanish, I didn't know german and french had polite or professional forms until I read this thread.

What I said, hopefully clearer:

Someone, you? mentioned "sir" and war movies.

If you are an American soldier, American upper level officers are called sir. They are officially gentlemen and to be addressed as such.

Commissioned officers, commissioned has a specific meaning you don't care about right now, upper level is good enough.

I would not be surprised if the tradition was old and shared with other places, especially places they speak english.

if you watch any movies with basic military training someone will be yelled at for calling a sargent(teacher, low level officer) sir, "don't call me sir, I work for a living," They worked their way up and are too low a rank, they are not gentlemen.

if parts are still unclear tell me which and I'll try again (or yoi can ignore it, you don't care unless you're joining the miltary and they will make sure you understand if you join.)

As someone said we appreciate your efforts and respect your scholarship, but you're mostly worrying about things we don't care about. We're simple and please and thank you and a smile are probably enough.

No one has mentioned that the US is huge and the english speaking world is even bigger. Details will change. Civilized people which most of us are will give you lots of time to adapt and won't expect mastery, especially of reagonal details from a visitor or someone new to the area.