Upvote:1
Your thesis is borne out by some "American" history, but a better source of instruction is post colonial, rather than "Native American" history.
South America is divided east and west, roughly 50-50 in terms of land area and population, between Spanish and Portuguese speaking areas. The Treaty of Tordesilles awarded "Brazil" to Portugal and the rest of South America to Spain. But most of modern Brazil actually extends west of the Tordesilles line, because that part of the country is climatically similar to the eastern part awarded to Portugal, rather than to the parts of South America with Spanish settlers described below.
The Spanish part of South America can be subdivided into two parts; the Andean highlands, and the southern cone. Much of the Andes is in tropical latitudes parallel to Brazil, but except for Venezuela, it is the "highlands" and not the tropics that define most of Colombia, Ecuador, Peru, and Bolivia. The southern cone (Argentina, most of Paraguay, Uruguay and most of Chile) are non-tropical lowlands that are neither highlands nor tropics, which makes them more alike than they are to either the Andean countries or Brazil.