As a native western Iowan, let me weigh in on the geolinguistics of the sandwich in question:
--"Loosemeat/loosemeats" is an extremely regional term only used within about ten miles of the Missouri River. It is absolutely true that Roseanne had no business using the term at Rosie & Tom's Big Food Diner; the sense of outrage is mitigated, however, by the fact that it's likely no one in the Ottumwa area had any idea what they were talking about. I grew up 100 miles from Sioux City, and I'd never heard the term "loosemeats" until I checked Real American Food out from the library. (We always went for Mongolian barbecue whenever we were in Sioux City.)
--"Tavern" is the preferred term in northwestern Iowa; however, a quick glance at the Immaculate Conception Parish cookbook from Cherokee, IA (ca. 1960) reveals that nearly every recipe for "taverns" includes ketchup and usually mustard. Another characteristic of the "tavern" recipes is that the meat is not fried, as in sloppy Joes, and not steamed, as in MaidRites or (usually) loosemeats; rather, the meat is boiled in the sauce. Generally speaking, a tavern is not quite the same as a loosemeats, but if anybody from Sioux City wishes to disagree, you're the experts.
--In central Iowa, "MaidRite" is the generic term for any sloppy Joe-like sandwiches, whether they're actually MaidRites or not. If you make a can of Manwich at home, you'd probably still call it "MaidRite."
--In eastern Iowa, however, most people seem to respect that a sloppy Joe is not a MaidRite, and they use the term "sloppy Joe" for anything made at home.
--In parts of north-central Iowa, the sandwich is question is frequently called "beefburger" and has more tomato flavor than a MaidRite or a loosemeats, but less than a sloppy Joe. While it's not my favorite variant for a sandwich, it is the best potato-chip dip ever.
--In the same region, the sandwich is also known as a "barbecue," which is also the term used in western Minnesota. The fact that people in the upper Midwest have historically called a sloppy Joe "barbecue" is why, in my opinion, you need to get off Famous Dave's back. You have to crawl before you can walk.
--In parts of southwestern Iowa and adjacent parts of southeast Nebraska, the term "Tastee" is used, but it usually refers to a slightly saucy, tomato-less sandwich. The meat is boiled, and recipes for this sandwich invariably include a crumbed-up hamburger bun as a thickener.
--A variant of the basic "tavern" recipe, made with tomato sauce rather than ketchup, and usually including a minuscule amount of chili powder, is popular as a hot-dog sauce. It's usually called "Coney Island sauce" (as it is many other places), but the resulting sandwich is never called a "coney;" it's always a "Coney Island." It's closest in spirit to Detroit coney dogs, but Iowa Coney Islands are sweeter and less spicy.
I'm no expert, but it's pretty obvious that, whatever this sandwich is supposed to be called, Sioux City, IA is its nexus, while western Iowa is where its DNA comes from. You could say that there's at least five different names for the sandwich; you could also say that there are at least five distinct sandwiches which cohere around the theme of seasoned crumbled hamburger on a bun. Obviously, what is needed is more research in order to find out the true history of this sandwich. If it can be called by five or more different names in such a sparsely-populated area, this is one for the culinary anthropologists.