The problem isn't with Tri Nations exclusivity, its to do with Argentinas comparative isolation, combined with the fact that many Argentine players play for french club sides, which has often raised the question of whether they should be admitted to the six nations as their players are in europe for much of the time.

I admire Argentina, especially after the last world cup where they were the only team that gave south Africa a run for their money and arguably the number 2 team of the tournament.

This despite not having "local" competition, as the so called northern and southern hemisphere teams do, to keep them on their toes.

Interesting to note that rugby was brought to Argentina by the Welsh, and in some parts of Patagonia welsh is still spoken.