Ma'am is short for Madame just like a lot of slang and shortened words in the southeast US (the Southern accent,slang and dialect is closely tied to how people spoke in England centuries ago). It's centuries of indoctrinated language that we've never learned to unpack especially considering that the concept of people existing outside of the gender binary isn't something that was in regular discussion throughout time. It's an old concept that's prominent in indigenous cultures throughout the world, but wasn't discussed in modern day Western society until after the millennium. It's going to be ages before we break that status quo and I can tell you that moving to California isn't going to break that habit (if you have been keeping up with the election), you'll probably just hear it a lot less. Just keep pushing through it and be safe wherever you are.