In the South East, they bring you sweetened (usually far too sweetened for my tastes) iced tea. This is amazingly universal.
I live in NC and have been probing the border for years.
For “nicer” restaurants, the universal sweet tea boundary seems to be precisely at the NC/VA border.
I once got a teapot with a few tea bags inside and one free water refill, I live in Poland and tea is rather warm/hot drink here
Even in hot countries people drink hot tea, it’s a custom in Turkey for example, in north Africa people drink hot coffee and it’s surprisingly effective in fighting the heat
One of my coworkers brought this Turkish coffee set to work and made me some Turkish coffee. It was so good
I think the difference is that the south-east us is humid as hell. You sweat and it doesn’t evaporate ever. The only way to cool down (outside or in the past) is to drink something cooling. Air conditioning was literally invented because typical coolers (swamp coolers) worked by evaporation, and it just didn’t function in the south east us.