I do not know much about South America which is why I am here. Since most were colonies, mixtures of many races and cultures and nearly all spoke the same language, how did it end up with so many countries? What separated them from each other?
Most countries in South America today roughly correspond to the borders of the Audiencias. Before I continue, I will give some clarity on certain governmental units within the Spanish Empire.
-Audiencia: a subdivision within a Viceroyalty serving as the seat of a court having jurisdiction over a specific area; also handled decision making in the absence of policy set by the Viceroy.
-Viceroyalty: had a direct relation to the king, unlike Audiencias, and could set policy for the entire viceroyalty; was treated as a province of Spain.
-Capitania-General: Created in areas deemed vulnerable to attack by local indigenous people or foreign powers and governed by a military governor; also had direct relation to the king.
-Governorate: even smaller subdivisions within Audiencias that handled local matters
-Intendencia: created during the Bourbon reforms; similar to governorates geographically, but with certain changes in their duties
The seat of an Audiencia could also serve as seat of a Viceroyalty or Capitania-General. Below is a list of countries with the corresponding Audiencia.
Ecuador - Audiencia de Quito
Bolivia - Audiencia de Charcas
I think what happened is that during most of Spanish rule, the Audiencias were by and large autonomous. So, the criollos from certain Audiencias, such as Charcas or Quito, who had just fought to govern themselves actually viewed it as a step back to form part of a nation that was more centralized than the Spanish Empire had been, such as Peru or Colombia.
Paraguay and Uruguay were both part of the Audiencia de Buenos Aires, but broke away. Paraguay broke away early on and was based on the Governorate/Intendencia of Paraguay. Paraguay had it own successful revolution independent from San Martin and Simon Bolivar that was sparked by the Paraguay Campaign. Uruguay roughly correlates to the Governorate/Intendencia of Montevideo, was invaded by Brazil during the Argentine war for independence and broken off after the Cisplatine War to form a buffer between Brazil and Argentina.
Brazil, at time of independence, actually consisted of three States similar to Viceroyalties and each had subdivisions called Captaincies. During the Napoleanic wars Brazil had been lifted to the rank of Kingdom equal to Portugal, but a revolution seeking a constitutional monarchy sought to force the royal family to return and strip away Brazil's equal rank. An heir left by the royal family to govern declared the independence of Brazil rather than submit and established himself as Emperor of Brazil. There were attempts in the early years by certain groups to splinter Brazil into smaller countries, but it seems the new royal house of Brazil had a centralizing effect and served as a rallying point for a unified Brazil.
I believe the answer can be distilled to Cultural; Geographical; and Historical and Logistical reasons:
- Brazil and the Guyana's are separate countries as a legacy of being colonized by the British, Dutch, French and Portuguese respectively instead of Spain.
- The spine of the Andes is an extremely formidable obstacle that divides the continent into a western spine; a central plateau and pampas; and an eastern other section Ecuador, Peru and Chile occupy the spine; Colombia, Bolivia and Argentina the central plateau and pampas area; Venezuela and the Guyanas occupy the Guyana Highlands and adjacent coastline; and Brazil the Brazilian Highlands and Amazon Basin. Similarly the Uruguay River and River Plata form a natural northern border for Argentina.
- The geographical regions described above are strongly associated with distinct indigenous cultures; and are the hinterlands of former provincial capitals of Spanish America. During the Wars of Independence launched by Simon Bolivar, in the early 19th century, the borders tended to settle further along natural geographic defensive positions, both as the rebels drove the Spanish off the continent in distinct waves, and as the newly independent nations squabbled amongst themselves for the spoils of victory.
- In cases such as the Chilean-Confederation War (1836-9), attempts to further unify the new nations were simply seen as too threatening by vested interests in neighbouring states.
South America was initially divided into the Spanish and Portuguese speaking parts by the Treaty of Tordesillas. The Portuguese part is Brazil, the Spanish part consists of most of the rest of South America.
The Spanish part was subdivided into New Granada (north), Peru (center), and La Plata (south).
The Andes Mountains subdivided each of these parts; e.g. Venezuela and Colombia in New Granada, Peru and Bolivia in the center, and Chile from the rest of La Plata in the South. The La Plata river itself spawned three countries around major cities: Asuncion (Paraguay), Montevideo (Uruguay), and Buenos Aires (Argentina.
The independence of New Granada was won by Simon Bolivar of modern Venezuela, of the south by Jose San Martin of modern Argentina, and of Peru, jointly between the two. Not even the "common" liberators was enough to keep the geographically separated pieces from going their separate ways.