The US Army has a long history working with the Austrailian Army, most notably in Burma during WW2 and Viet Nam. Viet Nam was a big learning Experience for the US as the guerilla type warefare was again new to the US. The Aussies on the other hand had vast experience in this type action, including the Malaysian uprisings and ongoing guerilla type terrorist attacks there. Some US commanders saw this, like Col David Hackworth, working in the delta region capitalized on this and sought Aussie's to teach his commanders how to fight that type of war.
The Aussies are fine soldiers, disciplined and commanded by astute, flexible and experience commanders.
My 2 cents...........