Update:
The rise of Purist Christianity in 15th Century Poland and Kiev can be traced to its defeat in Constantinople. The exile of the heretical Purist clergy from an increasingly Ibrahmist Roman Empire led to these same clergy moving to those nations, taking their wealth with them. Their numbers and influence led to the great majority of Christians becoming Purists, and a correspondingly more radical tone to the faith in those regions. Soon, the Patriarch of Lwow, as their leader, out of communion with Constantinople, styled himself, began calling for the driving of the blaspheming Muslims and the heretics out of Germany, and the liberation of the Holy Land from the heretical Emperor of Rome.
Eventually, the latter goal took precedence, and the First Magyar War, as it was later called, commenced in 1463. The combined armies of Poland and Kiev poured into Dacia, populated by Magyars who were still majority Purist, and met the armies of Emperor Basil X in open combat in the Crimea and around the fortress of Iasi. Around that city, the Emperor emerged victorious, but the Poles and Kievans plundered the countryside around it, for many years. The availability of long-range (300 meters accuracy) rifles on both sides led to the adoption of camouflaged clothing on both sides. Shining, plate-steel armour for horses and men was smeared in mud and paint, and the feathers and bright, fine clothing favored by officers became deadly. Even the Kings and Princes and Emperors wore no more distinctive markings than finger rings.
The Kingdom of Avaria, while letting soldiers march through its territory unimpeded (assaults on farmland and peasants were punished, however), tried not to get involved. In fact, by 1467, they had entered into an alliance with the Republic of Massilia for protection against both the Romans and the Poles and Kievans.
In North America, a massive outbreak of an influenza-like virus shattered the cultures of the Pacific Northwest. Polynesian traders arrived, carrying chickens as they did for long-range journeys. But the chickens and their owners carried a form of avian virus, one which the natives were entirely unprepared for. Within a decade, the single most deadly disease outbreak up to that point had decimated the Native Americans of the Pacific Northwest. Later Polynesian traders found nothing of value but fish, and soon abandoned their posts in the region.
An entirely different group of Polynesians, however, became the first mariners to cross an isthmus they named the Ikaukau. Their chief, who gave his name to the Isthmus, had learned from the locals that it was just a few kilometers across, and ordered their vessels taken apart and hauled on the backs of slaves and llamas (which earlier mariners had introduced after finding them in Peru) across the land. They soon found a vast freshwater lake, and sailed through it, down a river, and into another body of saltwater. When they finished crossing it, they journeyed north, where they were caught by Maya sailers in bronze-prowed canoes. The majority of the expedition was sacrificed, but the chief was spared, though branded with the mark of the King of Itza. Maya records documented this voyage, but it was not repeated for many years.