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.
NM here and it depends on the restaurant, many only have iced tea. But when you ask for tea you will be asked if you wanted sweet or unsweetened. If you say sweet, they bring you packets of sugar and a glass of unsweetened tea.
Fast food places will have both dispensers but mostly the sweet is unsweetened.
North Macedonia?
New Mexico