From The Atlantic:
Excerpt:
Today, the extent to which southerners are mannerly has evolved, as all things do. Some southerners lament what they see as a recent loss to their distinctive approach to etiquette, but this was already the case in 1897, when W. P. Trent wrote in this magazine, “We have seen that the Southerner’s basis of character is a fine one, and that he is becoming, year by year, more thoroughly nationalized.” He explained that “external manners have undoubtedly changed: there is now less suavity, less punctiliousness, less attention to small details, than of old; but this was true of the South of 1860 as compared with that of 1760, and means nothing but progress in the direction of greater freedom and individuality in conformity with the rest of the world.”
Part of the reason could be that more people are moving to the South. In January, I wrote about the disappearing southern drawl, another aspect of the region’s culture that is noticeably changing. I noted that, according to the U.S. census, the South gained more residents than all other regions combined from 2023 to 2024. I also found that the proliferation of the internet has undeniably altered southern culture; young kids are exposed to different behaviors on social media, and their role models aren’t just nannies or teachers or parents—they now come in the form of content creators and online friends.
These factors may be driving the shift in southern manners writ large. I’ve observed a generational difference even in my own family. My sisters still live in Tennessee, and I live in New York City, but none of us spends our days quite like our mother. She will make warm conversation with strangers whenever she possibly can. Living in a big city can often hurry me out of this habit. She’ll fill your plate a second or third time despite your saying you couldn’t possibly have another bite. I offer my guests a glass of wine and whatever nonperishable snack they can scavenge from the pantry. She will listen to a story she has heard hundreds of times with the enthusiasm of it being its first telling.
Politeness has never been part of Southern culture.
Minor quibble with @chronos point - I find/found during my time in the South that Southerners can be extremely polite so they can find the box they then fit you in. If the boxes overlap with their boxes, then they remain polite, perhaps more polite than the default neutrality or even brusqueness of the North East. Though sadly, they may only interact in terms of the definitions of said ‘box’. I had a few contacts with people in South Carolina and Texas that defined me as “Jew”, though they were supportive in the way some Christians are in that we are the “chosen people” that will bring the return of Jesus.
If you don’t overlap with their boxes, or they qualify the box as “other/wrong”, then they text to be far LESS polite. Or, maybe polite but absolutely refuse to engage with you other than that surface politeness, no matter your efforts.
YMMV, this is just my experience, and I can’t say that I’ve lived much in the ‘South’ past a half dozen summers (and much more in the Texas panhandle which I’d qualify).
I am southern. We’re just like everyone else. Many stripes here. Any number of personalities.
Bless your heart for bringing this up.
(I kid you. 
I try to be polite only because my Granny would rise outta her grave and take me in her sewing room for a little chat)
Is there an area of the country where Zoomers don’t act differently from Millennials who act differently from GenX who act differently from Boomers?
I think I do get “ma’amed” a lot less by the current crop of college students, now that I think of it. (It isn’t really part of my native culture, so I don’t particularly miss it now that it’s on the wane.)
I’ve mentioned before on the Dope about people from the South who are so insistent about how well-mannered and friendly they are, you get the impression they’ll beat the crap out of you if you disagree.*
Having lived in various places around the U.S., I’ve never seen significant regional differences in politeness and gregariousness. Probably it’s because of those durn northerners taking over everywhere. 
Maybe true to an extent in big metro areas, but I’d bet southern accents are alive and well elsewhere. It’s not a stereotypical southern accent, but the Kentucky twang is still prevalent in my area, especially if you’re shopping at Rural King.
*also the vibe you get from some Canadians. 