Thanksgicing dishes/sides are HIGHLY regional. I'm originally from Texas and growing up, you wouldn't catch butternut squash on our Thanksgiving table. I'm also guessing you wouldn't catch rice dressing (rice, onion, bell pepper, celery, pork & chicken livers) on a table in the Northeast or probably further west than Houston because it's kind of a Cajun thing, and most non-Cajun families down here are probably going to have cornbread dressing vs white bread.

In the Midwest corn was a big part of Thanksgiving dishes as well as the classic sweet potato and green bean casserole and the dressing was typically white bread and sage based. Oh and there were a lot more roasted root vegetables than I was used to growing up in Texas where the sides more resembled a barbecue: deviled eggs, potato salad, broccoli cheese rice, mac and cheese, collards or turnip greens.

I had a lovely Thanksgiving in Cape Neddick, Maine last year and their Thanksgiving spread had some things I was unfamiliar with but were probably more "traditional" than what I typically ate. Stuffing/dressing was definitely bready sage but had some nutty things, maybe chestnuts. Lots of winter squash based dishes, and some other stuff that I'm definitely forgetting.

All in all, Thanksgiving is about celebrating the harvest/bounty of the year so while there are some things that are mainstreamed/nationwide, it also makes a lot of sense to have some regional variations and specialties.