The evolution from feudal to nation states. With the later only truly supplanting the earlier after the Peace of Westphalia.
The colonization of the Americas, but mostly only the construction of trade forts and posts outside of it.
European domination not through superior land military, technlogy or the machine gun, but superior power projection and navy enabling them to have access to the entire globe to "butt into" local politics and take advantage of internal struggles. Europeans aren't able to take on a stable India, Japan or China, but unlike them the Europeans can travel and project power to whichever of them aren't stable.
Internal politics decided not by a nobility deriving power from land, but by courtiers deriving power from offices and positions as favorites. Nobles struggling not to acquire land, but trying to undermine the monarchs' current favorites and become one themselves.
An evershifting face of Warfare. From smaller armies with a focus on quality and dominated by heavily armoured men-at-arms living off the land, to huge armies primarily of pike infantry supported by a smaller cadre of elite heavily-armoured men-at-arms rampaging countrysides, to the "Cabinet Wars" of primarily professional infantry and noble officers leaving the civilian population largely untouched (at least by earlier standards) through extensive logistics networks, to the Levée en Masse of the Napoleonic wars reintroducing the huge rampaging armies, this time in the name of Ideology instead of Religion.
The changing nature of the struggles in addition to the armies fighting them, from the dynastic politics and wars of the 15th and early 16th centuries, to the Religious wars of the 16th and up-to mid 17th centuries, to wars as an "argument between Kings" of the later 17th and the 18th centuries, to wars as a method of deciding the face and fate of Europe in the late 18th and early 19th centuries.
The sowing of the seeds of the complete European domination of the Globe in most aspects. Seeds which only grew and bloomed during the 19th century after the end of EU4.