In OTL the Mohawk pushed the Mahicans out of upstate New York in 1628, thereby gaining access to Dutch (later British) guns. The Iroquois then pushed out out of their home in New York in the 1640s and 1650s and depopulated huge swathes of territory across the great Lakes. The Huron, Neutrals, Erie, the Shawnee and the Ottawa, plus various tribes from Ohio that are not known today (the blank spot you see on native American language or tribe maps in Ohio, is due to the Iroquois war). A mass diaspora to the western great lakes was one of the other major effects of the Iroquois war. The French with their Huron allies gone also suffered a major blow to their power and influence. The war only stopped when the Iroquois retreated back to new York after overextending themselves. They had gained a huge boost to their population due to captives (Northeastern Native American tribes usually incorporated captives into their tribe), and quite a bit of land.
The Iroquois war was probably inevitable, due to the mourning raids. The Iroquois traditionally went on raids to avenge deaths and give more strength to the tribe (yes, even natural deaths). Disease had cut their population in half, and therefore the raids had to be larger and faster, more wide ranging. But it didn't have to be as bad as it was.
So WI that went differently? I have two scenarios:
1) WI the Mohawk had not been able to defeat the Mahicans in 1628?
or
2)WI the Iroquois had been defeated in their rampage around the great lakes in the late 17th century/early 18th century.
In scenario 1) the Mohawk will have to be distracted by another tribe (I'm thinking the Huron) so that the Mahicans can gather the strength and then push the Mohawk to a stalemate. When that happens the Iroquois are likely to be squeezed. The tribes around them had access to British (the tribes to the south and east) and/or French guns (to the north and west). Therefore the Huron are likely to push in from the North and the Erie, Neutrals and others from the west. It's interesting to note that after moving to Connecticut the Mahicans moved to Wisconsin.
In scenario 2) the only way I'm seeing this happen is if the French go back on their policy of only having Christian Indians get guns. I don't think thats very likely, so perhaps if the Huron became more Christianized? Or in OTL the Huron were also the worst affected by disease. WI the Iroquois were also effected by a plague of smallpox in that era. If any of these situations happen, its critical to know when it happens. If the Iroquois are stopped early (i.e 1646, during the initial Seneca and Mohawk aussalt) then the Hurons will survive and things will probably revert to the status quo. If it's stopped later (i.e 1647-1655) then the Huron will have already scattered and the Ottawa and Nipissings will already be heavily battered. Later and the only effect is less migration to Wisoconsin and better winters for those there.
In all scenarios and sub-scenarios except the late end to the war, a major effect will be the level people in the Ohio. Settlers didn't realize it, but the Ohio they moved in to was the result of depopulation and then resettlement by other tribes, and the descendants of refugees. Therefore when settlers in ATL arrive they will find a more vibrant Ohio, with more villages, more cultures and less fractured. It is likely that there will be more alliances by the western tribes against settlers.