What's the latest that China could break up and the various regions undergo ethnogenesis similar to what happened in Europe?
I imagine anything in the 1800s or even 1700s would likely be too recent for concept of a United China or Chinese ethnic group to die off. If I recall correctly the Jin and South Song were going in the direction of a separate Northern and Southern Chinese identities before the Mongol invasion. Maybe something thing similar occurs in the 1600s with Ming keeping out Qing from Southern China and stalemate continues until the arrival of widespread European ideas see a separate Northern and Southern Chinese ethnic identity.
I imagine anything in the 1800s or even 1700s would likely be too recent for concept of a United China or Chinese ethnic group to die off. If I recall correctly the Jin and South Song were going in the direction of a separate Northern and Southern Chinese identities before the Mongol invasion. Maybe something thing similar occurs in the 1600s with Ming keeping out Qing from Southern China and stalemate continues until the arrival of widespread European ideas see a separate Northern and Southern Chinese ethnic identity.