I think after a cuisine or manner of cooking has been used in a region for almost a thousand years we are free to say it is authentic to that region, even though it was introduced. That you would deny Indians that, while accepting that Thai cuisine only started using chilli peppers in the last 300 years, opens a broader discussion about your personal understanding of culture and ethnicity.

Further, a Big Mac is a product made by a single corporation, lmao. I’m not going to justify that with further argument. But to use your Naitive American angle; a big part of NA cuisine is a bread called ‘bannock’. It can be savoury or sweet, and every tribe cooks it a little different from every other tribe. It is an important part of Indegenous cooking… and it’s an introduced food. The word bannock isn’t even from any native word. It came about from Scottish settlers/workers surviving on meagre company rations of flour and oil in isolated regions where they had no idea how to get food from the land. First Nations were introduced to it then found themselves in a similar situation as they were pushed off their land and given flour rations by the government so they wouldn’t all die. This all happened so recently my grandparents knew people affected by this.

It’s integral to their culture, even, and anyone who would deny bannock isn’t naitive would rightly be called an idiot by any indigenous person I know. Even though it’s an introduced food. That’s how culture, and food, work.