Regarding the Great Lakes, I'd like to sketch out a possible political balance. Feel free to pick apart any pieces that don't make much sense:
In the Great Lakes, there are multiple powers, all feuding for the valuable trade between the northern wastes of Canada and the more civilized feudal core. In these valuable trading points, alliances and conflicts are prone to change every few years.
The Commonwealth of Michigan is the prime power of the Great Lakes, being the single largest challenger to the Lakeleague's commercial dominance and holding a central position from which it can project military power more than any of its aspiring rivals. Detroit is not a member of the Lakeleague, and as such, the Commonwealth of Michigan usually acts in opposition to League interests. The only exception to this is when league interests would be useful against Michigan's two other rivals: the Commonwealth of Ohio(Michigan's primary land rival and enemy), and Genesee County, whose control of the Eerie canal has always been a danger to more westerly laker nations. Michigan remains the top dog, for now, but must constantly strive against the subversive interests of the Lakeleague in its own territory and act to keep Ohio as isolated from this prosperous trade as possible to maintain that dominance.
Genesee County, through its control of the Eerie Canal, is constantly in a state of low-level conflict with at least one of the Lakes' powers. Trade wars or actual military conflicts make that control hard to maintain, but the sheer value makes their position worth the expense, especially to maintain political independence from their supposed overlords in the State of New York. It's most common enemies are its nominal overlords in Syracuse, Michigan and her allies, and on occasion the Lakeleague itself will pull together the will to oppose their control of trade. They have lost and regained control of the canal several times now, and though they have currently regained it, Genesee must watch all of its rivals very closely or risk losing it once again.
The Lakeleague itself, a collection of small cities ranging from independent northern outposts to middle or small-sized nominal vassals of the States, Governates and Presidencies that surround the Lakes, is a rarely unified entity. The simple reality of their vast range of membership and allegiances means that, outside of making arrangements to keep money from trade flowing, there is seldom a united front that the Lakeleague takes against the various powers of the Lakes. When actions against that economic prosperity are taken, however, the Lakeleague has the power and influence to act as the ultimate kingmaker in any conflict in the Lakes. They are not to be underestimated in any conflict.
The State of Wisconsin once acted as the primary power of the western Lakes, with near total control of Lake Superior and as a stopover point for the fur trade from the Minnesotan and Canadian wilds beyond it. However, after the invasion of the Iowans and the conquest of the traditional powerbase of Madison, internal divisions have weakened this position. The governor currently resides in the city of Green Bay, and intends to extend gubernational control over the Superian trade through his control of the northeast and the peninsula of Superior. Milwaukee, a prominent member of the Lakeleague threatened by possible incursions of Iowan-sworn Chicago, Michigan, and even Ohio, is reluctant to surrender its own role in this trade as well as resenting the increased focus to the north at the expense of the southern former center of the nation. To the west, in the lands that we would call Minnesota, local small settlements and trading posts also feel alienated with Wisconsinite rule, and occasionally rebel or cause problems for the Governor. On the border, southern nobles clamor for an end to the tribute paid to Iowa and a war to reconquer the traditional capitol and lands of the State, hoping to return to their eminent position as the center of administration and trade through the state and church's power. Until these divisions are settled, Wisconsin can only act as a reactive player in the great political game of the Lakes, rather than an active player.
Iowa is only tangentially related to the Great Lakes trade, through its territory of Chicagoland, which traded allegiance from the Governor of Illinois to Iowa in a bid to avoid being sacked(partially successful). Chicago had always been the edge of the Lakeleague's trading range, and still retains a measure of independence from its influence as a result. Though it still remains a valuable market for the Lakeleague's selling of goods, it is only with the recent conversion of Iowa into a "civilized" nation focused on the former Illinois and its valuable trade and culture that it has begun to regain its influence in southern Lake Michigan. As Iowa shifts its focus away from destructive internal conflict of conquerors and conquered, Chicago could potentially become its own center of power in the Lakes. Unless, of course, the other powers act to cut it off before it becomes a threat once again...
Other powers include the Commonwealth of Ohio, County of Allegheny, and State of Ontario. Ohio, despite its large amount of territory on the lakes, rarely concerns its national government with the Lakes' problems. Ohio is generally more focused on its conquered lands to the south and holding the line against Iowan advances in the west, and is content to let the Lakeleague control its northern shores so long as money continues to flow into the Governor's pockets. The County of Allegheny also tends to favor the Lakeleague, but has several times made common cause with Michigan against the County of Genesee for control over Lake Eerie. Finally, Ontario, a state ruled by the Bishop of Toronto usually concerns itself more with the northern shores and other former Canadian states, but will occasionally choose a side in Lake politics for its own benefit.
Lastly, the northern shore of Lake Superior is full of local Canadian tribes. Some peacefully cooperate with the Lakeleague, but others act as commercial raiders, seeking plunder in the rich southern lands to bring home. These raiders make effective weapons by the various powers whenever war starts, and they are happy to take money from whoever is willing to pay the most if it so suits them.
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So, basically, I tried to keep with False Dmitri's Ideas: Lakeleague as a *Hansa, with Detroit as a royal competitor like Copenhagen, and Chicago as an edge-city of the trade range. I chose to explain the war map's warfare circle between Michigan and western New York as the conflict over Genesee's natural choke-point control over the lakes, with Michigan and Genesee having shifting alliances with the Lakeleague and neighboring minor powers as each war starts.
Wisconsin would act as the ultimate end-point of the trading system with near total control of the northwestern overland trade routes coming into the Lakes, but its isolated position surrounded by barbarians and raiders is as much of a curse as a blessing, plus I thought the loss of the traditional capitol and large centers of population(including La Crosse based on the map) would have a destabilizing effect on politics that others would take advantage of.
Ohio and Iowa, with their vast land-based realms, I imagined as more of a France/HRE/Poland analogue: focused more on land issues and willing to accept free trade city control of their northern shores the majority of the time as long as money keeps coming in. Plus, they should be far more involved with conflict with claimants over their conquered lands and not as willing to tangle with powers on another front as well.
Thoughts? Concerns?