@StoneyB and @Willow Rex have offered some useful observations.
I would like to add a few other points:
In my experience, in the US it is still generally considered polite, and largely obligatory, whether in the South or outside the South, for anyone representing a business establishment or a government office to address a customer or member of the public whose actual name the worker does not know as "sir" (for men) or as "ma'am" (for women). This applies to servers in restaurants, desk attendants in hotels, flight attendants and other airline staff, company customer service representatives answering telephone calls, police officers, clerks in government agencies, etc.
This also applies to interactions between adults who do not know each when one is trying to attract the attention of another in a public space, such as while riding on a bus, while waiting in a queue when shopping or when entering a business, etc.).
It is considered extremely rude to try to get someone's attention by saying something like "Hey, you," or "Hey, lady," rather than "Excuse me, ma'am."
("Madam" is very rarely used in spoken English. It is generally considered extremely formal and old-fashioned.)
Younger women and girls are still usually addressed in these situations as "miss" rather than "ma'am," while older women are addressed as "ma'am." There is no absolute rule for when a woman is too old for "miss" and should be addressed instead as "ma'am." (I was taught years ago that you should use "ma'am" for any woman who is old enough to be a mother. lol)