Northern hemisphere folk aren't much interested in southern hemisphere rugby despite the fact that it's usually much better! In fact, the overwhelming popularity of the Six Nations is quite a surprise given how many really poor games that tournament produces.
The sample is too small to establish if the converse is true but my experience would suggest so. Oddly, the only Kiwi responding appears not to know what rugby is.
Only a quarter of the people who claimed to follow the Six Nations follow any kind of non-international rugby. This tends to confirm my belief that below international level, the European game is a bit of a shambles. I don't have the data but I'd be really surprised if only a quarter of people who follow the Trinations, follow Super 14.