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.
US West: you get unsweetened iced tea unless they have hot and then they’ll ask. You can only get sweet tea at certain places and chains like McDonalds and Chick-fil-a.
I used to be a southern sweet iced tea drinker but now prefer unsweet.