Jonsk - In simple terms, money chases returns and flies from risk! Therefore there is not much the US can do atm imo.
The RBA will put up rates which will attract more investment pushing the AUD higher; things to make the USD higher are better economic news in the US, and lower unemployment (in the US) so that rates can rise.
You may have noticed that the Europeans, the Chinese, and others have been discussing a new benchmark to replace the USD. I don't have much depth on US monetary and fiscal policy so my short answer to your question would be that there is not much that can be done, but I'm not the Economist around here, lol.
Cheers, Pie (:
PS: Since I have posted this the AUD has gone from 91.33c to 91.36c.
