Anyhow, as far as the larger question goes, I think I would put those probably on the American side of the ledger, although they have some things in common with some of the thicker Sicilian styles, although nowhere near as doughy, with almost an inverse proportion of dough to sauce and toppings.
Pizza is one of those dishes that’s been adopted and adapted all over the world. The question is how different it has to be for us to consider it unique to a country or culture. Deep dish pizza was invented in the U.S., which either makes it uniquely American or simply a variation of the Italian original.
I understand that spaghetti with meatballs is a lot more common in the U.S. that in Italy, and that the U.S. version is different from the Italian version. Does that mean the dish is American or Italian?
They’re not, except for the derivation. Tex-Mex was something that sort of grew up on the border, with Mexicans and Mexican-Americans adapting N. Mexican cuisine to ingredients available in the US.
Fajitas were something that apochryphally came about when Mexican ranch-hands in S. Texas marinated and grilled undesirable cuts of meat (i.e. skirt steak) over charcoal and ate them as tacos. Eventually this was something that restaurant owners realized they could make and sell for cheap, and that seemed like it was a lot more classy than the standard cheese enchiladas, tamales and the like typically served in Tex-Mex joints of the day, as it is a sort of “roll your own” thing with pico de gallo, grilled onions, guacamole, etc… as condiments.
In reality, it’s very similar to the N. Mexican dish “arracheras”, but is a sort of Tex-Mex spin on it- I’m not to sure that cheese, sour cream or flour tortillas are typical in Mexico.
But ultimately, Tex-Mex and Italo-American favorites like our various regional style pizzas and spaghetti and meatballs are the same thing- local US adaptations of foreign dishes to take advantage of local ingredients (and a lack of scarcity in some cases).
Hell, even our beer is the same. Originally in the late 19th century, German immigrant brewers learned that to brew reasonably clear and light Pilsner-style beers with the local 6-row barley(high in protein and clouding potential), they had to cut it 20-30% with corn or rice, which is low in protein. This is where the original recipes for American lagers come from- they were more or less Euro-style up to WWII, when they were lightened in gravity, body and hops to appeal to working women, and they never recovered, being lightened and de-bittered even further in the next few decades.
But the addition of rice or corn was originally NOT a cost-saving measure- it was a deliberate decision made to try and get the beer right using local ingredients.
If it comes down to being possibly two different countries then America wins because we are awesome and we deserve it. 
It’s popular enough in England.
In season, corn on the cob is available pretty well everywhere, and you can get weird pre-cooked shrink wrapped stuff fairly well all year round. Dunno why you’d want to, mind, it tastes pretty nasty compared to fresh.
RI “Johnnycake” must be made with white corn meal-grown only in RI.
Pemmican. North American. EPIC bars are an excellent modern version.
Is Rhode Island even a real state? I think, in similar fashion to Pluto, Rhode Island should be down-graded to state-oid status and be positioned just off the southern tip of Florida, where it can be referred to as the nation’s pee droplet.
You missed a couple of our ‘inventions’. Google Meat Pie, Chiko Roll and Dim Sim. Or better yet…check this out! Oh, and like Russell Crowe, pavlova came from New Zealand. 
Historically, Australia’s cuisine was abysmal and was imported directly from the (mainly) British early settlers. Dinner was meat and three (overboiled veggies) breakfast toast (with Vegemite 
) or porridge, lunch was always a Vegemite sandwich when I was growing up! And not having any land borders with other countries, we didn’t have the privilege of sharing food ideas with neigbours. It was really only the post-wars immigrations (WW1, WW2, Vietnam War, Gulf War, Iraq War etc) that saw the miracle of new foods arriving on our shores.
Nowadays in the capital cities and many of the regional cities and towns, you can take your pick to either buy the fresh produce or eating at a restaurant from one of many different cuisines. Chinese, Vietnamese, Thai, Malaysian, Indonesian, Japanese, Korean, Mongolian, Indian, Greek, Turkish, Italian, German, French, Spanish, Russian, Jewish (kosher or otherwise), Chilean, Mexican, Moroccan, or an eclectic combination of two or more of the above! Shit, when I lived in central Melbourne, I could get ALL of those mentioned within either a 10 minute walk or drive. Even though I live in a regional town now, it’s still only a 20 minute drive to get to the specialty grocery stores for the essential ingredients to make my own stuff.
But as a foreign poster, my list of uniquely US foods are (in no particular order), the hamburger, peanut-butter and jelly sandwiches, pumpkin-pie, corn or clam chowder and cookies**.
** Only because nobody else in the world calls them cookies except for you 'Merkins, and because of the saturation of 'Merkin stuff across the world, my grand-children now ask for COOKIES in the BISCUIT section of the supermarket. [[shakes ancient and arthritic fist at the USA]].
Ok, well, now you’re just digging your country’s hole even deeper…
“Dim Sim”, “Chiko Roll” and “Google Meat Pie”? Who the hell gives names like that to food? …obviously Aussie’s do, and that’s my point.
“Dim sum” I can excuse. It’s a Chinese dish, and as we all know, Asians don’t have a good grasp of the English language (e.g. flied lice). But “dim sim” from a non-Asian speaking people? That’s just madness.
“Chiko roll.” Kind of a stupid name, but ok, wrap some dead chicken parts in a roll and call it a “chiko” roll—no problem. But, that’s not the case, my furry Aussie friend, is it!?! I did a little “chiko roll” sleuthing and discovered there’s no chicken flesh parts at all in a “chiko roll.” NO! You put **mutton **in your so-called “*chiko *rolls!” What?..you call sheep “chickens” in the land down under?!? That’s sheer madness! It borders on lunacy.
“Google meat pie”: [shudder] I don’t even want to think about what kind of horrendous, genetically malformed creature you Aussie’s call a “google” [/shudder]. I will not sleep well tonight thinking about it, I can tell you that.
Yeah, we call small, sweet, flattened dough disks, “cookies”, because that’s the name God intended for them to be called. I know you Aussies and you Brits think it’s cute to call them “biscuits”, but that’s a direct insult to God. His boy, J-dog, died for something of lesser consequence. Repent, heathens!
Biscuits & Gravy is a traditional Southern American breakfast food (i.e. it was sanctioned by Jesus himself). Take a good long gander at it. It’s mighty fine! Fluffy, cat-head buttermilk “biscuits” smothered under smooth pork n pepper white gravy! It don’t get any better than that, son.
You kangaroo rustlers want to pour pork n pepper white gravy over a couple of Nabisco chocolate chip cookies?!? You better have some money to pay the hangman, so he puts you out of your misery quick like.
I think I WOULD try this, but apparently Dr. Oetker doesn’t think Americans really would buy it, as I’ve never seen that corn pizza in my local grocer’s freezer.
I think their main point has nothing to do with corn but that “Big Americans” are “Crispy Outside- Soft Inside”
Trader Joe’s carries in its frozen section a Mexican pizza made with a corn masa base and refried beans, cheese, and various toppings. It’s actually quite tasty.