Well, you'll have to let me know when you're done!
As promised, here's a qbam of my idea. I also have a big wbam in the works, so that'll come eventually.
THE WESTERN CONTINENTS: TURTLE ISLAND, ANAHUAC, AND ABYA YALA
Point of Divergence: The cocoliztli epidemic arises before the arrival of Europeans in the Americas*. The plague spreads quickly along trade routes, but as a result, the adaptive immune system of Indigenous peoples is strengthened, better preparing them for incoming diseases.
ANAHUAC (Mexico)
In 1492, Christopher Columbus arrives on the shores of what he believes to be India. At the time, the Americas (they instead become known as Turtle Island, Anahuac, and Abya Yala) have a population of roughly 100 million, a fifth of the world’s population. Historically-speaking, Europeans were usually outpaced by the diseases they brought, therefore stumbling upon the smoking ruins of advanced civilizations. Where Europeans came with their diseases, Indigenous societies were wrought by plagues, which caused civil wars, which the Europeans took advantage of. This does not happen in this timeline.
While the Taíno, better prepared for Eurasian diseases, put up a greater fight, the Spaniards still conquer the Caribbean. As historically, the Spaniards enslave the Indigenous peoples there in mines and plantations, though a greater threat of rebellion means conditions are improved somewhat.
Eager for more gold, Hernan Cortés lands on the shores of the mainland. There, an empire led by the Mexica (Aztecs) are the fragile hegemon of the region. As historically, Cortés is almost defeated by the locals, but they are impressed by Spanish technology and horses and decide to ally with them against the Mexica. Together with the major rival of the Mexica, the Tlaxcaltec, Cortés marches toward Tenochtitlan. While a plague of smallpox spreads, it is much less lethal than historically.
Moctezuma II, King of the Mexica, receives the strange Spaniards. Cortés kidnaps him, holds him hostage, then murders him. Escaping the panicked city, the Spaniards join together with their allies and siege Tenochtitlan, sparking an all-out rebellion. Tenochtitlan is burned to the ground, but the Spaniards are greatly weakened from battles with the more numerous Mexica. With greater population and strength, the Tlaxcaltec are able to negotiate as the Spaniards’ superiors: in return for gold and permission to settle at Veracruz, the Spaniards will give the Tlaxcaltec their support and supplies of horses and guns. With this valuable aid, the Tlaxcaltec expand to be a regional hegemon over all Nahua people over the region. In their capital city, gilded with seized riches, the Tlaxcaltec leaders compete for political power and command of armies. Ambitious men seize power every few decades, though are soon checked by numerous rivals.
To the south, the Spaniards make an alliance with the largest of the many Maya city-states, Chichen Itza, with a similar framework as the Spanish-Tlaxcala deal: guns for goods. Chichen Itza expands through the Yucatan Peninsula over the next century, conquering its rivals and organizing an empire.
In Europe, less gold from the Americas and the spread of contagions from returning Spanish soldiers results in an unstable Spanish crown. Portugal and France press rivalrous claims to the Spanish throne; ultimately, Spanish colonies in the Caribbean are divided and the Treaty of Tordesillas is thrown out the window. Portugal looks for an ally of its own in
Anahuac, finding one in Tzintzuntzan. While a tributary of the Tlaxcaltec, Tzintzuntzan has mastered bronze technology and quickly throws off its imperial overlords once equipped with guns. In a number of wars, Tzintzuntzan marches east and comes close to sacking the city of Tlaxcala, but is repelled. Lake Texcoco, once the populous core of the Aztec Empire, becomes a ruined borderland of walls and fortress between the two competing powers. The independent states of the region seek security through cooperation. Teotitlan and the Mixtec, surrounded by the Tlaxcaltec and their allies, pledge allegiance to Tzintzuntzan. The Emperor in Tzintzuntzan has entered negotiations with the Maya to the east, hoping to organize an alliance to crush the Tlaxcaltec once and for all.
In the Yucatan, France and Portugal support rivals to Chichen Itza. Faced by drought, the empire collapses, but is reformed as an equal league between the city-states. Each city has connections with Europeans, hosting merchants eager to sell weapons.
Meanwhile, the Protestant powers seek to make money in the Caribbean. England finds an ally in the growing Nicarao Kingdom, which competes for control of the isthmus with an empire to the south, the largest polity in the world.
ABYA YALA (South America)
Francisco Pizarro, inspired by the success of Cortés, marches into the lands of Abya Yala in the 1520s. There, he finds a much more unified Tawantinsuyu (Inca Empire). With smallpox much less effective, Sapa Inca Huayna Capac survived his infection. Pizarro makes an alliance with Atawallpa, an illegitimate son of the Sapa Inca who was passed over as heir, and attempts to assassinate Huayna Capac in a diplomatic meeting. However, Huayna Capac survives, the Spaniards are repelled and the Sapa Inca leads a campaign against the newcomers and his rebellious son. Cortés and Atawallpa are defeated in battle; while the latter is captured and imprisoned, the Spaniards are executed or enslaved, their weapons and horses taken.
While Tawantinsuyu has cold relations with the Europeans for some time, they reach an agreement by the late 1500s and begin trading. Equipped with Spanish arms, Tawantinsuyu is able to expand north to the Caribbean and south through Argentina*. There, the Mapuche are either annexed as tributaries or displaced further south, though continuously raid into the Empire. Portuguese merchants introduce horses and wheat to the area, while farmers from the dominant Quechua lands make the area a breadbasket of the Empire. The Southern Region, Qullasuyu, was once an equal quarter of the empire, but now has a much greater population. The nobles in charge there are eager to exercise their influence over the capital city of Cuzco, and have been whispering to the Portuguese about a plot to displace the pro-Spanish Sapa Inca.
Along the coast, Portugal makes an alliance with the Tupi peoples, aiding in the formation of a league. The non-Tupi find allies in the French and Dutch, but the Tupi League already has a leg up on its rivals. Proxy competition lasts for centuries. At the mouth of the Amazon river, the Marajo Kingdom, an advanced polity with many tributaries, lasts through smallpox epidemics and continues to project its power into the local area, though is rivaled by the Tapajo and Xingu confederacies upstream. Marajo finds an unlikely ally in Latvia, whose attempts to build fortresses in the Lesser Antilles are successful.
TURTLE ISLAND (North America)
Besides Hernando de Soto and Ponce de Leon, Turtle Island (North America) does not have much contact with Europeans over the 1500s. Smallpox, nevertheless, spreads, but Indigenous societies recover, being better equipped from previous epidemics. Horses spread as well, diffusing from the south. The natives of the Great Plains quickly take advantage; they’re better able to hunt buffalo and form vast confederations similar to the khanates of Central Asia. The Apache march south and conquer the Diné, Hualapai, and other societies in the deserts to the north of Tlaxcala. Coahuiltec is brought under the fold as a tributary, while the Comanche are restricted to east of the Rio Grande*. The Apache are limited by the Rocky Mountains and by the many principalities along the Pacific Coast, who form an alliance of convenience to repel the Apache. The Yokuts, taking control of the Apache’s left-behind herds, continue to harass the coastal states, however. To the south, along the California* peninsula, Tongva and Chochimi conduct trade with Tzintzuntzan and other states in Anahuac, quickly making lots of wealth.
Other nations also take advantage of the introduction of horses. The Shoshone and Blackfoot to the north form vast confederacies, while the Niukonska (Osage) and Oceti Sakowin (Sioux) elect a unified leader to stop the expansion of a grand centralized state based in the city of Cahokia*, the Empire of the Mississippi.
With the arrival of French merchants on the Mississippi, hoping to sell guns for fur and gold, the Mississippian Empire is able to absorb neighboring nations and craft a vast tributary empire. Downstream, the Tula, Caddo, and Choctaw confederacies, buckling under the rule of the Emperor in Cahokia, hope to curry favor among one of France’s allies to sell them guns. Some local leaders have begun to stockpile them and negotiate in secret with Niukonska and Oceti Sakowin. [Cahokia is generally thought to have collapsed 150 years before Europeans arrived. However, there’s no reason the polity centered at that city could not have been recovered, especially if European diseases are less lethal. This is especially likely if Cahokia was a religious center as well.]
In the Southeast of Turtle Island, a number of confederacies and kingdoms buckle for control. With the expansion of empires from the west and another from the north, they’ll have to overcome their political differences to avoid annexation as well.
Centered along the south of Lake Ontario, the five nations of the Haudenosaunee (Iroquois) have marched in all directions to defeat the rivalrous nations increasingly armed with French guns. Backed by the Dutch, who were leased land to form the city of New Amsterdam, the Haudenosaunee absorb nations as far south as the Shawnee and Powhatan into a tributary empire. The French, cut off from lucrative beaver fur, doubled sales to the Empire of Mississippi, hoping to displace the Haudenosaunee. Along the Wabash River, Haudenosaunee and Mississippi fight battle after battle with no clear victory in sight. Many are caught in the middle of the warring empires.
To the northeast, the Wabanaki and Massachusett have formed a wide-reaching confederacy to ward off Haudenosaunee intrusion. They’ve successfully played both the French and the English at Plymouth for superior trade deals. While a peace treaty exists with the Haudenosaunee, the expiration is soon approaching, and both armies are preparing for war.
CONCLUSION
Contact was not all-bad or all-good. Crops were exchanged, blocking famines. Diseases travelled back and forth between the Atlantic, though greater viruses travelled with the Europeans. The Europeans also brought valuable tools with them. Horses allowed for the people of the Great Plains to better hunt buffalo and to form vast states to secure their independence. However, conquerors also rode on horseback, defeating those who failed to take advantage of the new mode of transportation. The arrival of firearms and, to a lesser extent, steel played the biggest role in changing interstate relations. Guns only grew more accurate, while steel made many weapons ineffective through armor. Those who were able to purchase those technologies from Europeans were able to conquer their neighbors, forming vast gunpowder empires comparable to their contemporaries in Asia. Without guns, the Mexica Empire fell, while the soldiers of Tawantinsuyu, armed with muskets, formed one of the largest empires that ever was. With greater power came greater intrigue and greater war. The low-intensity flower and mourning wars were replaced with vast campaigns and standing armies.
While the Western continents are going through their own Warring States period, the arrival of the printing press has brought with it a boom in intellectual production. Mythologies and religions are in flow, philosophers publish treatises read for kilometers, and ideas from Eurasia are digested through Indigenous lenses. However, as industrial smoke rises over cities in Europe, those who’ve watched the competition in the West with greed and hunger slowly and surely draw their plans of conquest.
(Names followed by an * are different in this alternate history, but for convenience as referred to as in our timeline)