[MyHonestOpinon]

The Americas were always going to be behind Euro Asia due to the shape of the continents. Going North-South you get big changes in climate and thus agricultural techniques and plants. Civilizations in the Americas could have spent thousands of years in a grow and bust cycle and never reach a similar level of development as the old continent.

[hax0ron3]

The East-West thing probably does confer an advantage, but it might be overstated. I'm not sure that the difference in required agricultural techniques between Mesopotamia and Europe was actually any smaller than the difference in required agricultural techniques between Mesoamerica and North America.