Does an international porn site like Pornhub take accents into account with their algorithm? Does an Australian watching Pornhub porn tend to get more porn with Australian accents than an American?

You're only going to have Australian accents in porn made in Australia or with Australian actors.

I was under the impression much of the modern (Western facing) industry produced on the American West Coast and Eastern Europe where young, pretty people come cheap.

I don't think there's enough Australian talent porn being produced (at professional grade anyway) to justify its own category.