Regional recipes such as Boston Baked Beans or Kentucky Burgoo would be interesting, especially if you could follow it up with a discussion about the region- climate, influences etc.
Another option might be to pick a European or other region and post a recipe typical of that community living in the US- such as a typical Pennsylvania Dutch recipe- then you can have a follow on discussion.
Shrimp & Grits
Yankee Pot Roast
I am American and really into reading cook books and I have never heard of any of the bolded. Unless Yankee pot roast is just pot roast, I guess. (Not to dis those things! I just love how diverse America is.
I know it's not, strictly speaking, exclusive to America, but I think Tex-Mex food like tacos, burritos, nachos (which are basically American) and even stuff like homemade tortillas or salsa is a good idea to show America's diversity. It's definitely not very European!
I love another poster's idea to post "Americanized" versions of Euro-originals.
I've heard the American idea of a big salad as an entree is pretty unusual over there, but I'm not sure about that. Would certainly make an easy recipe, maybe with something like a recipe for the very American ranch dressing.
edited to add disclaimer