They most likely would have become insular like china and stagnated similarly. Best scenario would be something like a south vs north dual empire constellation,

They most likely would have become insular like china and stagnated similarly. Best scenario would be something like a south vs north dual empire constellation, locked into a cold war that eggs them ever onward. But we will never know, because they did not produce a culture that could compete. Even with time to prepare, alot of these cultures abandoned advanced tech (https://en.wikipedia.org/wiki/Firearms_of_Japan https://en.wikipedia.org/wiki/Firearms_of_Japan) and supressed the "foreign" as the local elites felt there oligarchies threatened by those strange foreigners. I guess the usual attempts were made to encooperate the threat, by offering small kingdoms, slaves and positions within the ruling religion. It did not really work out, as disease crumbled the civilizations to dust. The other "prepared" culture (north american indians who met the vikings) did not take any lesson from that encounter either, because the tales of strange boats with christian raiders were not kept in writing and information was not exchanged with neighbors, with which they were locked in ritualistic inter-tribal warfare. Which is the main problem. The lack of information storage and exchange, due to a missing central culture. Africa had the longest time to acclimate to western intrusion, and did so by selling its own people as goods. The few things they did take over were weapons (used for slave trading and inter tribal warfare), the only candidates for organized resistance was the islamic world (who had writtings, a specialized labour system (industrial precursors) and centralized structures), but they were & are locked in by thee own cultural problems. Only exception were the persians, which were and are the france/us of the region. The chinese almost colonized africa, but then gave it up as a foolish endeavor, due to internal problems (starvation caused unrest) which was mostly due to there industrial revolution never reaching critical mass, which was mostly due to centralized culture/geography preventing technological competition aka harmony). There is good fiction on the topic https://en.wikipedia.org/wiki/The_Years_of_Rice_and_Salt https://en.wikipedia.org/wiki/The_Years_of_Rice_and_Salt, but you need basically a geographical reactor europes eternal boiling empire pot, with a progress state saving device attached (netherlands and england, some italian states were the scientists fled towards and from), to reach the critical mass. The ingredients were omnipresent, but the permanence of the societal reaction was hard to get critical.