How much culture is too much?

Okay, I hate to say it, but most of the books I read are American... there's just not that many Australian books that I'm interested in (most of the time when I think of Australian literacy I think of the boring school books we were forced to read).

I'm actually reading one at the moment, very well written and interesting (Steph Bowe's Girl Saves Boy) and I'm finding it very refreshing seeing the familiar landmarks and sayings (like, I'll just drop by Bunnings in the morning). Being Autralian, I'm very aware of what Bunnings is, and sometimes I even shop there if my parents need some timbre or paint.

But, how much culture can you put into a novel before it becomes confusing to the foreign audience? I'm often getting called on some of my sayings and Australian words that are unfamiliar to some of the audience who reads my stories, like doona

(hey, when I first started writing I wasn't aware that doona was known as a duvet in some places).

Sometimes it can be confusing, with different countries using different words to mean different things. I used to change things to make more sense (when I was starting out), but now I know that all the words that are different are a part of the Australian culture (and since my books are set here) I can't get rid of what's familiar with me.

So, how do you handle cross-cultural language differences?