But that would imply that people built the most elaborate culture at the first place they stopped. I am saying it is more geopolitical. That region of Central America seemed optimal to them and allowed them to build a more elaborate civilization. Why was their no Greece or Rome in Scandinavia?
Case in point would be the Comanche, a branch of the Shoshone tribe which originated in the Wind River area of central Wyoming. Their mastery of horsemanship was a game changer which allowed them to conquer most of what is now Texas, Oklahoma, Kansas, Colorado and New Mexico. While this did not keep them from ranging outside their normal homeland including northern Mexico, eastern Texas, Arizona, Utah, the Nebraska panhandle and even their ancestral homelands in Wyoming, it did encourage them to center their civilization in that area which they felt most suitable, namely the Texas panhandle.
By any measure, there are thousands of square miles of hospitable climate from the Pacific Northwest all the way down to the northern frontiers of Aztec civilization, none of which produced the advanced levels of settlement as the tribes named in the previous post.
As to your question 'why was their no Greece or Rome in Scandinavia?', the simple answer is the ancestral Vikings never produced a level of civilization even close to comparable until they came in contact with more advanced civilizations.
It is an argument you really can't make if you subscribe to the Bering Straight migration theory (exclusively or even mainly) as everyone is following basically the same route and, thus, contact would be inevitable.