Oh my gosh, this thread! This is what I do, this is my job!
I'm a buyer at a fancy deli in Kent and now that I'm there we do all sorts of American Foods! The biggest hurdle is the price, so very sadly, we have had to discontinue so many wonderful lines like Saltines, Graham Crackers etc due to a lack of interest. We still carry Lucky Charms, a variety of Aunt Jemima (syrup, pancake mix), Zatarains (no Gumbo) Hersheys syrup, corn syrup, marshmallow fluff, Oreos, Clamato, pickles, relish, grape jelly, ranch dressing etc. I don't want to look like I'm advertising, so if you want the name of the shop, feel free to pester me.
Oh, and I saw earlier on that people were looking for proper parm, romano and provolone - that's something else we do. Sadly, the provolone doesn't come in slices, it's proper chunks
Also, another thing to do is to get in touch with some of the importers and they can point you in the direction of where they distribute their goods. If you google 'American Food Importers' or 'Distributors,' it'll come back with some of these places. I've just done it and recognized some names.
I'm sorry if this is vague, I didn't want to look like I was advertising. Like I said, feel free to get a hold of me if you'd like the details - I'm happy to share.