Memes

Yeah, apples aren't native to the New World and apple pie wasn't invented in the Americas. It's not specifically British, either; it seems to have emerged independently across Western Europe in the middle ages, and was first brought to the Americas by the Dutch rather than the English. Hell, not even the quintessential American pie apple was invented here; the granny smith is Australian.

The British invented roast turkey about as much as they invented roast bison. You want to get into more specific recipes, I'd say chicken tikka masala is British and chicken parmesan is American, but I'm not letting the British have right of way over "get bird, add heat."

Pumpkin pie is kind of a strange one; the first thing you'd call a "pumpkin pie" was more of a savory soup eaten by Dutch settlers in Massachusetts in the 1600s; the first pumpkin served in a pastry crust was French, and the modern pattern of "sugar pumpkin puree in a shortbread crust" was invented a few minutes after the US Constitution was ratified.

Sweet potato pie is less ambiguous; it seems to have popped into existence fully formed in the American south in the 18th century.

Basically all corn products including popcorn and cornbread were known to the Native Americans for thousands of years before Europeans arrived.

The first known recipe for cranberry sauce as we would recognize it today was written in 1796 in the United States.

Green beans are native to Central America, green bean casserole was invented in New Jersey in 1950...

Again, what of this is particularly British? An American thanksgiving meal is as British as pizza.