Because if nothing else, we are a grown up country that needs to throw off the vestiges of colonial power and control. As for being an ally of the US, that's a choice we have, who would want to be allied to the Brits, given they abandoned us several times in the past.Throwing away the symbolic yolk of colonialism will do absolutely nothing to change that - do you seriously think things would change for the better if we were a republic?
We're just someone else's vassal, that's all. We never have stood on our own two feet and we probably never will. It was like getting a seat on the UN Security Council - who the frig do we think we're kidding - we're nobodies. We probably couldn't even beat New Zealand in an air or naval conflict.
New Zealand no longer maintains a fighters or bombers in its Airforce so a bit over the top.
Australia's military budget is the 13 or 14th largest in the world at 1.5% of GDP, Australia's GDP is the 12 or 13th largest in the world. As % of GDP it is a bit low compared to those around us, going by them we should be up around 1.8%, same as France but lower than UK at 2.2%.
The difference between Australia and the bulk of the top 10 military spending is that we make very little of our own hardware so the others like USA which spends 3.3% actually have a large domestic military support R&D and manufacture industry's so the money isn't being burned in the same way. So to go higher, we need to start doing more R&D and manufacture of military hardware or risk hurting the economy that funds it. For example to match France in % of GDP, we need another $5 Bpa.
The Republican movements may issue with the current system is that the Head of State for Australia is not and can never be an Australian. There are not too many countries left in the world that still operate this way.
In the OECD group of countries, NZ, Aus and Canada are the only ones with a foreign head of state.
Perhaps the most benign way to become a republic is basically to retain exactly as we have now, expect the GG just gets re-titled the President, after all its worked this far and the Queen has no input into Australian politics so whats the difference?
Canada went one step further than Oz in the 60's and dumped the old flag for the Maple Leaf which is without doubt 100% Canadian and recognized by all as such. NZ is currently going down this path now and looking at the options I'd say they will dump the current flag in the 2016 referendum. Australia has looked at doing the same for sometime, however we keep getting stuck on "we went to war for this flag". I suppose with the likely change in NZ, we will no longer be confused with them anymore.