Oddly enough, many Canadians use the word "American" to refer to Unitedstatesians, so presumably they'd use it to describe cuisine that same way (as in, poutine is Canadian but disco fries are American). This is extremely analogous to the Asia conversation, in that of course people know the term comes from the continental scale, but using that scale is less common, so it must be specifically invoked.

And then you've got Puerto Ricans, who are definitely US'ian but eat more like the non-US'ian Americans, so who knows what they would think of if you ask about American food, but it wouldn't surprise me if Contiguousunitedstatesian is the default (i.e., the same cuisine the Canadians would be referring to).