Moreover, if they had had domestic horses and camels, would the cultural and technological exchange have been akin to that of Eurasia, or the north-south axis of the continent would still have inhibited it to some extent?
Neither of those premises can really be put forward as the sole, or even the primary, reason. Mountains and animals do not dictate human civilization patterns, and they never have, despite what coffee table books might suggest to the contrary. This line of argumentation is called geographical determinism and it is rarely, if ever, supported by evidence across time and space. See: