What would have happened had Temujin (Genghis Khan) had failed at unifying the tribes of Mongolia, and never went to the Empire Building/ Conquest spree that he did? How would the world have changed with out the Mongolian Empire?
You've also butterflied the Black Death, which means that feudalism will stick around longer and Europe will be far more prone to famine and internecine warfare (yes, even MORE so than OTL). You've definitely delayed industrialization, or at least its prospects of starting in Europe.
Industrialization in Song China, however...