What you mentioned at the top basically explains the difference between serving Americans/Canadians and Russians. I’ll spend an entire night chatting with Americans which some have told me is more of a thing in Canada but I think it depends on the state. I chatted with a couple from (I think) Michigan today for a while after they had already paid and I could have finished my shift. The other week I served a group of Russian guys and they were friendly but definitely more about their “tribe” like you mentioned. They were never rude but I don’t see them striking up unnecessary conversation either. I brought them a new pitcher of water before the other ran out and got a surprised smile for that though which I have yet to understand. Some people would probably consider that rude I guess. When I was a cashier we were suppose to make conversation with guests because it is considered rude/awkward not too.