Not everybody is a xenophile, some people are nationalist types who get annoyed (rather than aroused) whenever they hear a foreign accent, and may even have trouble understanding them. You're not going to change channels if you hear an American accent, but they very much will if they hear an Australian one.

One out of every six big US movies would be black if it were proportionate to population, but they're not. The reason is because black people will watch white movies, but white people don't watch black movies. It's the people willing to walk away that make the decision.

It's very expensive to redub a series just to change the accent; they're getting a return on that.