Carrie's Mom and Chamberlain, Maine are two sides of the same coin! There's a reason why Carrie is able to opt herself in to the in-group by putting on makeup and a pretty dress and pretending Prom is the most important night of their life and laughing at the popular boy's racist jokes! The second she starts doing these things, the entire school community starts to accept her as one of their own! Sue Snell's entire arc revolves around her suddenly being treated like Carrie was always treated because she said "you know what? why do we instinctively perform cruelty in order to maintain this order? what is it we're actually so afraid of losing? it's all bullshit, it does not matter at all. high school doesn't matter. my high school sweetheart is probably not the love of my life. why do we care about maintaining our role in a hierarchy that ends forever in two months?" and decided she wasn't going to prom.
The idea of suburbia as almost a living thing that depends on everyone's unwavering submission and professed belief pervades the entire narrative. Chris Hargensen is upset at Carrie for "stealing" what she thinks is the most important night of her life, she's mad at Sue for not being upset about losing prom, because everything about her is empty and hollow unless everyone pretends that Prom and The High School Hierarchy are the most important things in the world.
And, crucially, Carrie is not the high school's innocent Omelas Baby whose subjugation is presented as necessary to the rest of the school's happiness. She's an outcast because of her mother's sheltering and abuse, and because this small town harshly punishes anyone who challenges the idea that Smalltown Suburbia Is The Most Important Thing Ever. She walks around telling everyone they're going to hell for doing normal teenager things, all the while desperately wishing she could do normal teenager things. It's crucial to the plot that Carrie would pretty objectively be just as bad as any of her classmates, if the shoe was on the other foot.
Until the cruel prank that set off Carrie's powers and her rampage against both her mother and the town, she was being rapidly accepted as One Of Them, all the while the girl who was on top of the social ladder was quickly and suddenly ostracized and bullied because she no longer cared about prom or gossip or the epic highs and lows of high school everything. It's about the idyllic concept of a Wholesome All-White Suburban High School being a twisted myth, not because it hides a dark secret, but because the concept itself is sinister!
And most importantly, the whole ending of the book is about how the town died after The Black Prom. It became a ghost town. With the illusion ripped away, and no more true believers to uphold the cult of suburbia, the whole thing crumbled into ash. None of the high surviving high schoolers married their sweetheart and became townies who had kids who repeated the suburban smalltown cycle. None of the local businesses that survived ever recovered because they were too dependent on the myth of suburbia, and without people who believed in that, who the hell was going to patronize them? Why would anyone keep up this Gilmore Girls charade, when what they've been through makes it impossible to give a shit about High School Football?
It's why every interpretation that tries to give Carrie some distinctive physical trait, be it appearance or race or weight or what-have-you, that the other kids are bullying her for, misses the mark. In order for half the themes to scan, Carrie absolutely needs to be able to join the in-group simply by saying "actually, I give a shit about this!" and then acting like she gives a shit about it. It's important that Carrie and Sue be able to very easily switch places in the social hierarchy because that's what happens in the book!
