I spent a bit of time abroad with people foreign to the US
Pointing is VERY rude! My one friend (from Thailand) would always point to people when speaking about them. It was just very uncomfortable and I didn’t realize it was part of the social structure here until she was doing it everywhere lol. Don’t point at complete strangers and talk about them, you may end up starting a fight
The American South, while known probably to some for being racist, is VERY VERY big into politeness and manners.
Generally do things like hold the door open for others, a cashier may ask you “hi how are you” just answer “good, how are you?” Or “I’m okay, how are you” but whatever you answer remember to return the ask. Always say please and thank you. If you make eye contact with a stranger give a smile and a nod. Unless they say hi, then say hi back. I also tend to end conversations with people by saying “have a good one” if meeting somebody (more of a professional thing) when shaking hands, let the person who initiated the handshake introduce themselves first.
Also Americans tend to be very friendly and will strike up conversations with people, don’t be afraid to chat, just don’t bring up politics