Haussler is 100% Australian. He was born in Australia and grew up in Aus. You should know this since we've been through it before with Oliver.
What identity he considers himself to be is his affair. Whether he's 100% Australian or not is irrelevant for this, of course. Half of his family is from Germany, and it is generally impossible for someone whose roots are so far apart to not feel allegiance to both sides to some extent. So, he clearly isn't '100% Australian', but he has made the decision in recently renouncing German citizenship, so that it is safe to assume that he considers himself more Australian than German. In view of the fact that most of his formative years were spent there, that's perfectly understandable.
What identity he considers himself to be is his affair. Whether he's 100% Australian or not is irrelevant for this, of course. Half of his family is from Germany, and it is generally impossible for someone whose roots are so far apart to not feel allegiance to both sides to some extent. So, he clearly isn't '100% Australian', but he has made the decision in recently renouncing German citizenship, so that it is safe to assume that he considers himself more Australian than German. In view of the fact that most of his formative years were spent there, that's perfectly understandable.