While the Treaty of Tordesillas did indeed establish boundaries in the New World for the quarreling European powers, it's most important impact was the precedent that it set in dealing with the peoples that already occupied this land. Throughout the process of establishing this line of demarcation to separate the lands, the whites failed to consult the Native Americans for their input. Natives were not invited to the negotiating table. For whatever reason, the mercantile powers of Spain and Portugal did not recognize the sovereignty of these peoples over their own land. They felt that the indigenous populations were uncivilized and unworthy of the lands that they had lived on for thousands of years. While estimating the number of people that lived in the Americas at the time of Columbus has been a daunting task for historians, even the lowest estimates calculate the population in the millions. Essentially the Treaty of Tordesillas violated the sovereign property rights of these million inhabitants. The Treaty foreshadowed future European treaties and political maneuvering that would eventually cost the native peoples their entire continent.
The most important result of the Treaty of Tordesillas was that the area that we now call Latin America was divided up between Spain and Portugal. Spain was given by far the greater part of this area. However, the treaty did allow Portugal to take control of what is now Brazil.
After Columbus “discovered” the New World, the Spanish and the Portuguese started to argue about who should control any new discoveries. They eventually got the pope to negotiate a compromise between them. The pope at the time, Alexander VI, was Spanish and his decision favored the Spanish more than the Portuguese. The Spanish and the Portuguese then negotiated further and the line dividing the two territories was moved farther west, in favor of the Portuguese. When they came to an agreement, they signed the Treaty of Tordesillas.
The most important result of this treaty was that Central and South America were divided up between Portugal and Spain. Spain got most of the land, but the line was far enough west to give Brazil to Portugal.