A few concepts.
-Egypt never unifies or remains divided in various smaller kingdoms longer. There is no Narmer or unification of the Naqada III culture-or this process is delayed substantially. Perhaps as long as a thousand years. Which gives time for the formation of other polities in the near east, and delays Egypt as one of the pillars of ANE Bronze Age civilization.
-Revolution in France, I had an idea of republican opposition to Napoleon, along those lines, let's imagine a small cadre of Jacobins and other French revolutionaries fled around the time of the directory, and return in 1817 or 1820 or so. The Bourbon monarchy botches the invasion of Spain or otherwise becomes unpopular, and a revolution against it happens again. Now there is a few ways this can go-intervention by the powers can lead to it being reinstated(most likely) or renewed revolutionary wars. The former is liable to end in the victory of the coalition and France is likely to be dissolved and carved up. In the latter scenario, war has changed-I suspect the aim of this new revolutionary france would be to spread revolution to the german states, Italy and the low countries, while securing defensible borders.
-Total Hapsburg victory in the thirty years war. Basically Wallenstein is given a blank check, and the Imperial armies are reorganized with the pro emperor nobles bullied and bribed into line. The Danes are smashed and Sweden defeated with Adolphus dying ignominiously on a Baltic shore. The French are defeated and Cardinal Mazarin is overthrown, with a much worse Fronde. Spain holds the Netherlands. The power of the Emperor is increased with Catholicism remaining a force in northern Europe, this has plenty of butterfly effects from the Spanish empire not declining as quickly to a more effective Imperial resistance and counter attack against the Ottomans in the later part of the 17th century. Basically Germany becomes more centralized under Imperial authority.
-Horses survive and are domesticated in the Americas. I have not seen a timeline that deals with this concept with much thought. But let's do so. The paleo indians do not hunt american horses into extinction(though they do still cross into Eurasia), they are eventually domesticated first for food and hide, and then are ridden. Different breeds of horses emerge in different places. Though not all Indian cultures have them. And in some they remain as either food or status symbols. But firstly this allows the great plains to be settled more broadly faster. As before horses most indian tribes remained on the edges of the plains. Secondly nomad invasions-lots of them into mesoamerica and the like. Though of course horses in Mesoamerica change the logistical constraints of mesoamerican empires. No Aztecs and any similar polity will be able to expand further-and exert larger control over subject tribes and cities. In the Andes horse breeds that are hardy and can survive at higher altitudes emerge, less need for runners. In some ways horses make the Amerindians more stratified, with an emerging aristocratic class that can afford to maintain and ride them. In terms of the European conquest-horses make the process more complicated. They do not halt it. If whatever mesoamerican empire the spanish(or whoever) finds has horses-the fear of them no longer exists. This doesn't change the differing natures of warfare(though it might) or guns. It does mean Cortez can't charge into a mass of indians and see them route because they fear the strange deer. Horse raids on the english colonies especially in the early years cause greater losses-though the Virginia company was dead set on colonization, and would basically pour infinite resources into it. No matter the cost. Horses also change the environment, less forest and more open areas. And the way of course Indians interacted with it. Perhaps they develop a more eurasian form of forest management and agriculture, perhaps not.