So, apparently Argentina not only has a national Rugby association, but it is well supported by its people as well. Argentines are more european than people from other South American countries due to a huge immigration of European peoples throughout Argentina's history. Due to this influx of European blood and heritage in Argentina, the people tend to be physically larger than the people from the other South American countries; thus permitting them to participate in a sport as physical as rugby.
Mr. Girodano has sent us a video of the Argentine National team preparing itself during the national anthem (himno nacional). These Argentines are quite proud to represent their fatherland.
This wikipedia article may also interest you. It explains the roots of Argentine rugby, and elucidates just how popular it is.
Highlights of Los Pumas.