Easier terrain on the Middle East & Mediterranean would have helped the spread of writing, IMO.
The old Old World had several civilizations that grow near each other--Egypt, Fertile Crescent, Greece. Surely this proximity and ease of travel (assisted by water transport and pack animals) would have promoted contact and learning.
The ancient Americans were separated from each other by jungles and deserts, and lack of means of transport.
Jar, if you read Jared Diamond's Guns, Germs and Steel, your question would be settled. I think it's one of the most informative books ever written.