Argentina is the second largest country in South America and features a little bit of everything, from mountains to coastline. Its national team reached the Quidditch World Cup quarter-finals within the last century (QA8). The Patagonian desert region of Argentina was also host to the 2014 Quidditch World Cup (QWC).
Lexicon list of Ministries of Magic
From the Web
The official name of the country is the Argentine Republic (Spanish: República Argentina) and it is located in the southern half of the South American continent (Wikipedia).
Writing by J K Rowling on WizardingWorld (Pottermore):
Writing by J K Rowling on Imgur (Daily Prophet coverage of the 2014 Quidditch World Cup held in Argentina, originally from Pottermore):