For some reason, Woolies don't stock them anymore. And we only seem to have 3 flavours now in Coles. The US has over a dozen flavours and other products, and some interesting ones too. The products page on the US site lists heaps (and makes crunching noises when you pass your mouse over each), but may auto-direct back to the AUS page, so just re-select the US country page.
(pringles is one of the regular food items I 'sample' every year while in america for botcon - pizza is one of my fave flavours)