Nationality..?

I was in a coffee place today in outer suburban Melbourne with my 4 kids, and I struck up a conversation with the women who work there (no, this isn't typical). After we'd exchanged a few pleasantries, one of them asked 'excuse me, but what's your nationality?'

On one hand I was quite chuffed that even though I'm fourth-generation aussie, and went to high school about a mile from this coffee place, they thought I was an exotic foreigner of some sort - I did quiz them, of course. They thought I was german, or possibly swedish, On the other hand I was vaguely worried. I've lived outside Australia for 15 of the last 20 years, am I losing some fundamental Australian-ness? A girlfriend I had in the US (who was barking mad, but that's a different story) thought I looked very Australian indeeed, but that was because of my prominent chin and sticky-outy ears.

I'm going to the footy on Monday, I wonder if that'll help.