In Great Nations there are several smaller, hardly recognizable points of divergence in the first half of the 19th century, mostly 1806–1848, that resulted in some very different outcomes in the second half, leading to a world today we would hardly recognize.
The main effect of 19th century European philosophy and politics is the prevailance of nations. People assign themselves (or are assigned) to a shrinking number of nations depending on, chiefly, language, culture, economy, territory, tradition and religion. The prime reason for wars since has been the unification of nations. The most prominent and effective politicians have been those that managed to shape or broaden the idea of their nation and thereby influencing the course of action of their and affected peoples.
Over the course of the past two centuries a handfull of nations became superpowers, hegemons on their continent, some longer than others. While the German Reich steadily and slowly gained more and more influence, today being almost synonymous with Europe, the British Empire and the Russian Cardom both collapsed shortly after gaining world dominance for very different reasons. In Eastern Asia, the Mongol Neo-Khanate quickly transitioned into Great China and later became the Japanese Genroinate, but merely changed the the elites. Hispania likewise shifted its center of power several times and never regained a role like it had in the post-columbine era. Africa (and the Middle East) has yet to see an intrinisc major power, after the Osman Empire (Great Nations) collapsed and Pan-Islamism failed so miserably.
There never have been “world wars”, because stable ententes or coalitions would only form for national-cultural (not tactical) reasons, e.g. between imperial powers and their (former) colonies, and such conflicts hardly ever rose. The most devastating war in history, however, was the Second North-Atlantic War (1952–1955), although the Indochine War (1982–1990) had an even higher death toll.