Hesperia was one of my first alternate history maps. It is based on the premise that the expedition of the Vivaldi brothers in 1291 actually manages to reach the new world. They name it Hesperia and the Italian city states take a lot of the new territory. Due to the earlier contact the difference in technology is small so the native tribes manages better the in our timeline. Under the pressure from the Europeans, the Hesperians form several confederations with different levels of cooperation and were so far able to contain further expansions by the newcomers. Imagine large squadrones of Cherokee and Apache fighting against hardened condottieri.
Although the map is in German I don't think most of it is easy to understand.