If you stop European colonization, you do so by extending Mongol colonization. You remove the conquistadors, the Tlaxcalans find themselves stretched out over the Aztec altars with their hearts on the menu. You take out the European powers, China eventually takes southeast Asia and crushes the cultures there by forcing their culture on the local people through the pen and the sword (mostly the sword, most likely).
Humans are bastards. Unless you change human nature, stopping colonization is impossible. If the Europeans don't do it, someone else will and the results will be about the same.