The meatball sub is what the regional meatball sandwiches become once they are detached from any region: a national template, standardized by sandwich chains and pizzerias from coast to coast, where the build is a fixed specification rather than a local argument. Meatballs in marinara, melted mozzarella, a soft sub roll, often a quick pass through a conveyor toaster. The defining feature is consistency, not character. A meatball sub in one state is engineered to taste like a meatball sub in another, because the whole point of the format is that it travels and reproduces without a local baker or a pizzeria oven behind it. That portability is the sandwich's identity, and it is what separates the generic sub from the New England grinder, the Philadelphia hoagie, and the New York parm hero, each of which is defined by a single thing the chain version deliberately smooths away.
The craft, such as it is, is in making a saucy sandwich survive a standardized line. The roll is soft and uniform, sized to a fixed meatball count so the bread-to-filling ratio is the same every time. The meatballs are usually a pre-cooked, portioned product held in marinara, which keeps them consistent and lets a non-specialist assemble the sandwich quickly. The mozzarella is a low-moisture shred chosen because it melts predictably under a short heat pass rather than for pull or browning. A brief toast firms the roll just enough to hold the sauce for the length of the sandwich without the structural ambition of a grinder's hard-toasted crust or a hero's broiled lid. Everything is calibrated for repeatability over peak quality.
The variations are mostly menu options rather than regional codes. A provolone swap, added peppers and onions, a spicier marinara, a footlong against a six-inch, a baked version finished in a small oven for a browned top. The chains differentiate at the margins while keeping the core specification stable. The grinder runs the meatballs back under heat on a toasted roll, the hoagie holds the sauce back behind sharp provolone, the parm hero browns mozzarella in a deck oven, and the upstate red-sauce meatball builds go their own way, and each of those deserves its own article rather than being crowded in here.