History is filled with the stories of the successes of great leaders, and their conquests that have shaped history to the present day. In two countries, France and England, two men were once in command of a turning point in their respective histories. These men, Hugh Capet in France, and Cnut of Denmark in England, could've had very different lives. Lives that, instead of the two united nations we know and love (or, for some others, loathe) could have resulted in shattered lands.
987 AD: Hugh Capet, King of the Franks, loses his position to Charles of Lorraine after the Capet-Carolingian War of 987, returning the Carolingians to rule in West Francia. This would result in further decentralization of power in the region.
1016 AD: Edmund Ironside, King of the English, lives a considerable deal longer than otl. He uses this time to plan to resist a Danish takeover should he die before Cnut the Great.
British Isles: The place of England is taken by the competing states of Wessex and Jórvìk, each vying for an advantage over the other. Each would attempt to expand their influence into Wales and Ireland, going to war several times. Scotland would emerge stronger than otl, taking advantage of the conflicts.
France: The Capets are reduced to Counts of Paris, rarely succeeding to the Francian Throne after the days of Hugh Capet. Inheritance allows them Orleans and Berry occasionally, only to lose one or the other later. Brittany, Normandy, Aquitaine, and Burgundy would be the chief competitors for the throne for centuries. Many French Noble houses (such as Valois and Dreux) in ATL bear names of the otl houses that were cadet branches of the Capetian dynasty. But this is merely a coincidence, as the Capets slid into irrelevance, other families took the names of their lands for their families.
Holy Roman Empire: As in otl, the HRE decentralizes into hundreds of states, but is joined in this fate by Francia. The two empire would clash in several wars, with members of one fighting for the other many times.
Iberia: Aragons power expands as it fulfills ambitions in southern Francia, eventually gaining an electorate vote with Toulouse. It and Portugal are more prosperous, while Castile, lacking an ally in France, suffers, and as such fails to conquer Granada.
Russia: Novgorod is able to defend itself against Muscovys rising power, yet unlike Muscovy, never expands beyond the Urals. It fights various wars with the Nordic countries over its ambitions in Finland and Karelia.
Balkans and Asia Minor: Byzantium is still unable to hold back the initial ottoman advances, and loses most of its territory in Asia Minor. Yet it is able to survive.
The rest of the world changes through the butterfly effect.
Notable Differences from OTL
1. Central and Western Europe is awash with small, independent states, accompanied by a number of larger countries on the perimeters. Attempts by outside powers, like Denmark, Castile, and Wessex, to bring some of these small states into their fold would be resisted by these larger states, who see Francia and the Holy Roman Empire as "their" domains. Aragon would be a tolerated (albeit often strained) exception.
2. Aragon's success in building a Mediterranean empire would enable it to resist Castile's expansion. It's long independence would create a national identity separate from Castile.
3. Continued exploration of the New World (though less successful settlement) by the Vikings would introduce various European diseases to the native populations. While the impact would be of a similar percentage as otl, the native peoples build a resistance before the rest of Europe learns of the new lands. Many countries only get so far as forts on the coast, though countries like the Hansa and Luxembourg manage to establish larger territories (see New Hamburg and New Netherlands).
4. Byzantium's nigh-constant wars against the advancing Muslim armies of the Turks and Arabs disrupt trade with India and China. The relative isolation from from the two ends of the civilized word (east and west), prevents the sharing of ideas that spur technological advancement. As such, technology could be described as a century behind modern OTL.
5. The Far Eastern empires of Japan and Ayutthaya find opportunities to advance their interests in Asia in the face of a considerably divided Europe. They would prop up satellite governments as a barrier between them and what colonies the Europeans establish. Meanwhile, they extend their reach to the New World themselves, following Zheng He's fleet there.
6. Due to the nature of the differences between OTL and ATL people and families, people that don't exist in our timeline begin appearing around 1100 (mainly in Wessex and Jorvik). However, the effects of the POD spiral to the point where (with a few exceptions) there are next to no people from OTL present after a point.
7. Nationalism takes hold mostly in the Slavic states, leading to the Ruthenian Compromise in Poland and the Austro-Bohemian Compromise of 1959 in the Habsburg monarchy. Byzantium's collection of a multitude of ethnicities, and failure to accommodate, would lead the Balkan War of 2008.