I'm actually surprised at the amount of 'chit chat' which occurs during screening in the US.

Yes, at MUC and other places I am often greeted in a cheerful manner, with a pleasantry or two. But there isn't commentary whilst I am being patted down, or my bag checked, other than questions or statements directly related to the issue at hand.

It does seem however based on my own experiences and experiences reported here by others that TSOs have a lot of leeway in making comments to travellers. I don't mind a pleasantry but some of the endless chit chat that occurs seems to divert attention away from the task at hand.