Some more spoilery maps for my roughly-planned projection of Where the River Flows (tl link in signature).
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As mentioned in the previous post, Misia and the other countries of the Northeast are all quite developed nations in the modern era, and are economically and militarily tied through the NAU. Misia and Takamcook are constitutional monarchies (Takamcook's head of state is the British Crown) while the rest are republics. They are mostly religiously Midewin with significant Christian minorities (Takamcook is Christian majority) and even a Jewish minority that fled from persecution to the New World. Many individuals hold both Christian and Midewin beliefs.
After horses, guns, and steel were introduced to the New World, Misia started expanding east into the plains, while the Aztecs started expanding north into Northern Mexico and east into Mayan lands. Due to the brutal nature of the Aztec's sacrificial practice, many people began converting to Christianity. Following a bloody civil war, the Christians overthrew the government and the Anawak Republic was born. Although it was originally a radical puritanical theocracy, it since transformed into a more secular state. The Mayans would gain independence only in modernity.
Alaska was formed as a result of Russian imperialism, although it was never really settled and remained native majority, mostly being used to trade furs. This would also be the case with the Lushootseeds and Kalapuyans further south, who would expand into the plateau against the nomadic tribes that had adopted the horse. Today, both countries are diverse developing nations largely propped up by the NAU in order to use their Pacific ports.
The Southwest was historically disunited due to the arid and mountainous terrain and the lack of horses until the Navajo Empire managed to conquer its neighbors once horses made their way to the region. As Misia and Anawak made their way towards the Southwest, the empire came to collapse into civil war. Both sides took land for themselves, mostly dividing it north and south. However, this territory was never assimilated, and both territories would gain independence in the modern era. The former Misian state was known as Ashipewahk, an ancient Misian exonym meaning "Cliff Land/Country" referring to the great cliffs and mountains and the Pueblo people who lived in them. The former Anawak state was called Aztlan, the legendary Nahuatl name for the lands to the northwest where the Aztec people originated. The borders of theses states, while following certain geographic markers, did not reflect the cultures within them, and so the political system quickly broke down. A Navajo dictatorship quickly became dominant in Aztlan, while the Nuchus (Utes) and Sosonis (Shoshones) fought for power in Ashipewahk. Eventually both countries fell into civil war. Ashipewahk was divided into Sosonia and Nuchua. In Aztlan, the Kutsan people, historically an independent, isolated, and united civilization based around the lower Colorado River and Delta like the Ancient Egyptians, rebelled and formed an independent state, which while relatively more stable than the other states, still became a corrupt dictatorship. All four countries are dictatorships with constant domestic strife and international tension. Misia typically has to deal with refugees come from their western border as a result.
California I have an idea for the lore but I haven't fully fleshed it out so I won't put anything here for now. I haven't decided if I want it to be a united state or a bunch of small ones or a battleground between Misia, Anawak, and Russia.
What would become Muisca land was conquered by the Incas, but eventually gained independence following the empire's decline.
All of the countries with their OTL names were founded through colonialism like OTL (including Colombia, which is now mostly Venezuela).
Hispanola was the first colony established by Spain under Columbus, who destroyed the native Kingdom of Ayiti and commit genocide against the local Taino population, although many would be able to flee as refugees. North America and the Inca Empire would eventually come to host Taino diasporas. The Taino managed to thrive in diaspora, becoming successful as merchants and bankers. This was especially useful in the Inca Empire, as their knowledge was applicable to the Incas who sought to transition from a centrally-planned economy to a market economy in order to modernize. In the late 19th Century, the Cayanist movement (from the Taino "Cay" meaning "island") sought to return the Tainos to their native homeland in the Caribbean, many of which were still controlled by Spain. The movement would go on to successfully establish the State of Ayiti, which would come to dominate the Hispanic state of Hispaniola. Today, Ayiti is a developed nation with close ties to the nations of the NAU, although there are many human rights concerns over their continued occupation of the remaining Hispaniolan territories. They tend to receive frequent condemnations from the Global League, with calls to withdraw their occupation and establish an independent Hispaniolan state (Essentially, Ayiti is is a Taino Israel, a state formed by an returning exiled indigenous people who commit numerous atrocities in rebuilding their homeland).