I wouldn't get too concerned just yet.
If American power is on such a decline, relatively, on its own - then the medium term solution is for its allies to 'step-up' and add their weight to contribute significant military compability, in order to retain, collectively, influence that once was possessed by the US, individually.
Alternatively, even relative power decline by the US means that the potential for strategic over-reach is significant and therefore it is incumbent upon Australia to ensure its ability to give even a 'great-power' a bloody nose (if not actually, 'ripping an arm off') by itself. The perceptions of risk and cost of an attack are the fundamental elements targeted by defending forces in deterrence strategies. The intent would be to make an attack on Australian as unattractive a proposition as possible.
Brett.
Yes with an american decline in power on the one hand and the ascendancy of chinese power on the other,coupled with chinas sheer size of numbers,and one would think eventual economic parity with the west/first world,then yes aus needs to grow a capability to bleed or dismember a part of such an opponent,and yes an effect that would give an opponent pause to consider such an undertaking in the first place,one would hope.
Im not concerned yet,well not too concerned,but in the not to distant future the potential outcome of such a event does make me feel uneasy....