If you could change a single part of pre 18th century history what would you change?

I'm looking for specific and non obvious answers. Give me something visceral, rid the world of a figure or nation you hate. Preserve a culture you adore. It doesn't have to make sense either, you are basically god here.

What I mean is don't just say you'd get rid of imperialism or colonialism bc no shit

Personally I would make it so that the Americas are never discovered by the old world and every "would be" conquistador (especially cortez and pizarro) explodes.