I understand that WWI was a complex issue mainly dealing with North America, Europe, Africa, Australia, and Asia. However, Brazil did help out the Allies by sending weapons - do they represent South America in the continent count, or is one country too insignificant?
At the beginning of WWI, the German Cruisers led by Vice Admiral Maximilian von Spee fought and sank two British armored cruisers off the coast of Chile. A month later, Spee tried to raid the Falkland Islands, but they were surprised to find a British Force of two Battlecruisers and five regular cruisers. The battle was a disaster for the Germans with 2,200 dead, including Spee and his two sons. In 1917, Brazil declared war on the Central Powers, but they were the only Latin American country to actually do any fighting. Panama, Guatemala, Nicaragua, Costa Rica, Haiti, and Honduras all officially declared war, though their involvement was minimal.