Colonial governance, production systems and transportations routes heavily shaped the economic and political development of the region well in to its post-colonial era of independence.
The Western Hemisphere has been dominated by the United States since the start of the 20th Century.
South America has struggled to produce a regional leader partly because no single country embodies the necessary qualities to become one. Brazil has the most potential, thanks to the size of its of territory, population, natural resource deposits and economy. Argentina is a counterweight to Brazilian influence in.
The modern governments are actually young and relatively inexperienced democracies. They are still refining their social contracts with their citizens.