The Dutch Revolt.
A country of only several million, divided into multiple administrative districts, rebelled against the Spanish Empire before its real terminal decline. I know the Netherlands were extremely wealthy and urbanized, and that they weren't actually at first rejecting the Spanish monarch but Philip II's efforts at the Counter Reformation and centralizing, but still. After William the Silent's assassination and England failed expeditions, the Netherlands were in a bad position. Spain then focuses on failed effort sin England and then France, giving the Netherlands time to recover, organize, and reclaim lands for near a decade. During the rest of the war, the Dutch savaged Portugese and Spanish colonies, started to dominate the East Indies Spice trade, and overall entering their Golden Age where they had more merchant ships than all of the rest of Europe (I think?).
The Netherlands had much of the financial, economic, and industrial foundation for this series of events, but the growth from 1550-1650 can't be understated. The Eighty-Years War would probably be classified as a wank in a TL on this site if it hadn't actually happened.