Clearly, you've read Guns, Germs, Steel, whose accuracy when it comes to anthropology is on the same level as the (Christian) Bible's accuracy with respect to cosmology.
> Americas on the other hand lays on the north-south plane, Isthmus of Panama is narrow to pass through, variances in climate and terrain greatly limited communication and commerce between north and south.
It should be noted that there is rather little evidence of technologies spreading along the main East-West axis of Eurasia (particularly Neolithic technologies), while there is far more evidence of such technology spreading along the North-South axis of the Americas. For example, pottery may well have spread from its invention in the Amazon Rainforest across the Caribbean to Mesoamerica and the Southeast US; corn did spread from its initial domestication Mesoamerica to both the US (where it largely supplanted preexisting domesticants) and down into the Andes (where it supplemented the existing potato crops); and metallurgy spread from its Andean origins along the Pacific coast to Western Mexico and the Southwest US.
> Americas on the other hand lays on the north-south plane, Isthmus of Panama is narrow to pass through, variances in climate and terrain greatly limited communication and commerce between north and south.
It should be noted that there is rather little evidence of technologies spreading along the main East-West axis of Eurasia (particularly Neolithic technologies), while there is far more evidence of such technology spreading along the North-South axis of the Americas. For example, pottery may well have spread from its invention in the Amazon Rainforest across the Caribbean to Mesoamerica and the Southeast US; corn did spread from its initial domestication Mesoamerica to both the US (where it largely supplanted preexisting domesticants) and down into the Andes (where it supplemented the existing potato crops); and metallurgy spread from its Andean origins along the Pacific coast to Western Mexico and the Southwest US.