Start with South America's geography,focusing on the Southern section,specifically -Brazil.
South America has always been relatively isolated compared to other continents,including Africa. Sea traffic tends to stretch across the whole northern hemisphere - from North America across the Atlantic or Pacific Oceans to Europe and Asia. Africa is connected to the other continents that surround the Indian Ocean or byway of northern Africa to the Middle East and beyond.
But southern South America (the Southern Cone-from Rio de Janeiro south )finds itself off the beaten path. Even traffic with North America tends to focus on the states that are in the proximity of the Caribbean.
Within South America,you have the twin barriers of the long mountain spine of the Andes(highest mountain range in the world next to the Himalayas) running the length along the western coastline with intersecting narrow valleys connecting regions on either side. And the huge Amazon rain forest to the north with it's east-west bisecting river system.
The distance between Rio de Janeiro and New York City (4,776 miles) is the same distance as it is to Portugal (4,651 miles). The result is that the southern cone states are as isolated from their northern neighbors as they are from countries across the gulf of the Atlantic. Even within the continent itself,historically,exchange of ideas and goods have not been easily transmitted,particularly on the north-south axis.
It is that long north-south axis that creates the difficulty.It means that South America spans several climate zones,from tropical rain forest in the north to a polar environment in the south,making it difficult to transfer food crops and animals from one zone to another.
The temperate zone encompasses a very small section of South America compared to the majority lying in the tropical zone - one reason for many of the debilitating diseases the countries continue to face.
And of course,the difficult to traverse Amazon rain forest that acts as a barrier stretches laterally across the continent making it difficult to trade either ideas or goods between the north and south regions.
That isolation coupled with the United States' disinterest in the region has shaped Brazil and her relations with the United States and even though Brazil is no longer isolated - the mindset that was formed by those circumstances continues to have an affect on our relationship and world events.