Will Ships be able to travel from the Atlantic Ocean to the Great Lakes? I mention this because of Chicago which is America's second largest city and the fact that many submarines that served in the Navy were built in shipyards on the great lakes ( 30 submarines from Wisconson's Manitowoc Shipbuilding Company)
There were some mods of HOI3 which changed the (unpassable) lakes to naval zones, and made the St Lawrence seaway from a river also into a naval zone. This allowed naval units to move from the Atlantic to Chicago.
In that situation, if the devs did it in HOI4, Chicago would be coastal and allowed to have dockyards.
The only problem with the mod is that capital ships couldn't get through the locks on the upper reaches of the seaway. Anything built above a certain size was stuck in the Great Lakes. Only subs and some smaller vessels built at Chicago could reach the Atlantic.
The ship you pictured, USS Wolverine, was an old 1912 side-wheel passenger steamer built on the Great Lakes, which never sailed out of them.
It was bought by the USN in 1942 and converted to a "carrier" purely for training exercises. It never saw combat, and wasn't designed for operational roles. It had no guns, nor any below deck hangar, nor was it fast enough for modern planes to reliably take off which required a reasonable headwind. Some days it couldn't be used for training because of this. Operational carriers would turn and go full speed into the wind to generate enough lift for planes like the Hellcat to take off. The old paddle steamer with the flight deck on top could make only 19 knots, while the USS Enterprise for example had a top speed of 32 knots. The pilots could train only if the wind on Lake Michigan was strong enough.
So, no fleet carriers were ever built in the dockyards on the shores of the Great Lakes. Nor AFAIK anything the size of a BB or BC, or even a CA. I guess the capability of the dockyards was there, but no operational requirement to protect US shipping on the Great Lakes when the only other country with access to them is friendly.
The modded version of the game would have allowed Germany to send it's subs into the Great Lakes, and even land transport ships there. It would work only if the devs hardcoded a Kiel Canal type mechanism to get from St Lawrence to the Great Lakes with a special rule limiting the size of ship, and a Panama Canal type rule preventing all ships unless you control the provinces on either side. But I think the same rules would also have to apply to get from Ontario to Erie, then Erie to Huron, and Michigan to Superior. For little value to the game.