Don’t know about the “cheesy/theme” qualification, but I’ll add Stuckey’s and Black Bear Diners to the list.
Haven’t encountered anything like you’ve described, but I would think the quintessential American franchise would be the sort you stop at frequently during cross country drives, and that would be Denny’s. Which made for quite the juxtaposition of imagery when the one near Reno was invaded by all the people leaving Burning Man 
For example, I arrived in full body paint with mud in my hair…
The biggest portions I ever had were at Claim Jumper, and some chain whose name I can’t remember that had a southern poverty motif.
Would that have been PoFolks?
A lot of them have “ethnic” themes. Chillis, Outback Steakhouse, Olive Garden.
I have to say my GF and I ate in a Chillis a few months ago when we were visiting a friend in Pennsylvania. We were sort of disgusted by the ginormous portions of fried food.
No that’s wasn’t the place, but it is the exact kind of place it was, a ripoff of that I think. Maybe something about a junker or a junkyard. Like I remember the chicken fried streak was a signature item, and it was good, but it literally covered the whole 12 inch plate, and the sides were on a different plate.