The only Countries with their own sub-forums have top-level professional club rugby teams in them (bar Japan and Spain...kind of), that we talk lots about anyway. That makes Argentina no different from the likes of Samoa .
Maybe the management can provide you with a different answer, but thats the way I see it.
If there is enough demand for discussion about Argentina then a forum will be added, this is only a trial, we want to see whether posts increase during the non typical International Season