I think some people don’t realize that this is just a human (possibly American) thing no matter who you are. I am a white male with Southern heritage all the way down yet I live in New England and I work in an industrial facility that is very much blue-collar and multi-ethic (primarily people of Portuguese descent but we have examples everything). People ask me where I am really from all the time because I obviously don’t have a New England accent. When I reply ‘The South’ or, more specifically, Louisiana, the questions really start because my accent and attitude don’t match the Southern stereotypes either. I don’t take offense by it because they are all just being curious and really want to learn something about how I came to be here. I developed a short explanation about how my mother was from Texas and a teacher and she never let her kids develop a really strong Southern drawl but plenty of my friends growing up could curl paint by opening their mouth because theirs is so strong.
There is plenty of prejudice against Southerners too and I have to restrain myself every time an ignorant Northerner goes on a long screed about Texans in particular because half my family is from there (my graduate school adviser was particularly offensive and unapologetic about that). However, I always love a good Southern or redneck joke (there really are plenty of stereotypical ones in real life; bless their little hearts) and the others generally do too.
In my case, being a white, straight, male, Protestant, American isn’t even enough for people to find some small difference to either question or rib you over and I believe that is true for everyone. Most people don’t mean anything offensive when they comment on someone’s red hair like my mother has and I can see how the cumulative effect can get old just like cashiers that have to hear the same old jokes many times a day but there is generally no harm intended. It is usually just someone trying to be friendly and failing at it like all of us tend to do sometimes. In my experience, the difference between someone saying something awkward and being an asshole is a clearly bright line. ‘Microaggressions’ aren’t common at all because most people aren’t that subtle or nuanced. In the vast majority of cases, people are reading things into common behaviors that aren’t intended or implied because people sometimes say dumb or awkward things even when they mean well.