With what US routes is there automatic meal service in the economy (coach) cabin on the legacy airlines and low cost carriers? Which routes provide meals for purchase?

I would presume that meals are provided in the front cabin of a 2 cabin plane, or the front 2 cabins of a 3 cabin plane, on most domestic US routes?

I would presume that meals are served (in the rear cabin) from the mainland to Hawaii, and Alaska. I would presume that meals are served (in the rear cabin) for flights (of a certain minimal duration) if the destinations are Canada, Mexico, Caribbean (including Bermuda and Bahamas), and Central America?