Are Roast potatoes not a 'thing' in the US?
I don't think they are, sadly.
I always do roast potatoes though. We have them on all the big occasions apart from the Fourth of July.
I basically serve an Irish Christmas dinner for Thanksgiving, with a few nods to American traditions and some omissions from the Irish side, and we have the same but with roast beef at Christmas.
I've never tasted, let alone served the sweet potatoes with the marshmallows. exMIL, homecoming queen of her high school, circa 1949, and in a great many ways a poster child for Norman Rockwell's America, never did either. I boil them, mash them with butter and molasses and S&P, sprinkle finely chopped pecans on top, dot with butter, and put in the oven for a few minutes.
For veg I do green beans, carrots, Brussels sprouts, and roast parsnips. ExMIL always served cauliflower, carrots, and green beans, mashed potato, no parsnips. Also cornbread stuffing, which tasted too sweet to my tastebuds.
I do Mary Berry's/ my mum's sage and onion stuffing, with added chestnuts, and I use cubed baguette, not breadcrumbs.
No celery, no cornbread, and it goes into the turkey for roasting.
I've seen photos of American friends' 'dressing' which seemingly gets boiled in a saucepan with turkey giblets added. Not for the faint of heart...
For dessert at Thanksgiving we have pumpkin pie, and for the second year in a row we'll have pecan pie too. For Christmas we'll have those two again, plus mince pies and tiramisu, possibly a baked chocolate pie and/or a pavolva, and a variety of cookies. I do tiramisu because it's the closest I can get to a trifle - the DCs are not keen on traditional Irish sherry trifle. They don't care for traditional Christmas cake either, or plum pudding, and it's too much bother to go to just for myself.
I make cranberry sauce with cranberries, orange juice, a little grated orange rind, and sugar.
My local classical music station always plays this around Thanksgiving 
'Lime Jello Marshmallow Cottage Cheese Surprise'