The more I think about it, the more deeply convinced I am that the (primarily? exclusively?*) British phrase "macaroni cheese" reflects how French the English of Britain is. It doesn't look so on first sight, for there is nothing French about either word in it. But the construction fits the model introduced to British English by boeuf bourguinion and spaghetti bolognaise. From that perspective, the construction of [main substance][sauce] makes sense.
But I can't think of a similar explanation for "macaroni and cheese". All of the [substance] and [substance] standard constructions I can think of are pairings of more substantial things than a dish and its sauce.** Sauce is something that's with, not and, as far as I can think. I can't think of any other and examples involving sauce offhand in American English.
* Of the four people who claimed otherwise on the poll, all but one unknown have definitely lived in the UK for a substantial period of time.
** Unhelpfully, the examples coming to mind aren't American. Bangars and mash. Bubble and squeak. American more often hyphenates multi-content dishes: strawberry-rhubarb pie. Apple cranberry juice.