If you are living in America, and you want the food made by the people in your community who are Chinese, would it make sense to call it Chinese food?
Chinese food, as in: the food the Chinese people make.
Italian food, as in: the food Italian people make.
Indian food, as in: the food that Indian people make.
America is a country made up of immigrants from other countries, so when they are here making the foods that they used to make in their home countries, we call it "Chinese food", "Italian food" etc.
I understand why this can be confusing to people who aren't used to living in culturally diverse countries. It is normal in The United States to interact with people from all over the world. Saying "Chinese food" does not literally mean food from China, it means food made by Chinese immigrants to The United States.