While your list is true, it's not a great list to make your case. One responder said that the hamburger and hotdog don't fit, because they're German, but that's only appreciably true for the hotdog (which is effectively indistinguishable from a bockwurst).
Gumbo, jambalaya, barbecue, cornbread, chili, clam chowder, fried chicken, pancakes, biscuits and gravy, pies (any sweet sort, not just pumpkin), cheesecake, brownies, fudge. The US is also one of the three great pizza countries (along with Italy and Argentina).
And that's just the some of the stuff that's relatively decisively American. In practice, as I said in my original post, things are incredibly fluid, and a lot of American dishes are heavily based on other cultures, and a lot of other cultures' mainstays are based on New World ingredients. American and Italian versions of "Italian" cuisine significantly co-evolved, and it's virtually impossible to separate one from the other.