The pact's timing also seems more about political weaknesses than strengths.
Canberra has been bullied by China over trade in the past two years. Australia has now thrown its lot in completely with the US, despite America's decline over the past two decades as an international political and moral leader with its wars, struggling democracy, and doubts over its reliability as an ally.
After a coronavirus response that has got away in two key states, Prime Minister Scott Morrison - who faces an election in the next year - appears to be waving a nationalistic card that his domestic opponents will find hard to bat away.
The UK is trying to emerge from a disastrous pandemic and establish an identity as a global power independent of Europe after Brexit.
The pact helps the Biden Administration to turn a corner after the chaotic withdrawal from Afghanistan and show Americans its next path. At home, President Joe Biden's agenda is struggling in Congress, and coronavirus case numbers remain high.
Australia's promised nuclear-powered subs can stay longer at sea and move faster. But their arrival will be pushed further into the future.
And Australia will be locked in tight with US military operations as a key cog in the region where the two most important countries in the world face-off.
That's a major change to Australia and New Zealand providing long-distance support to the US during America's wars. This time it's like having the Cold War in our back yard. The Deputy Sheriff has a shiny new badge.
China has been in bristling defensive mode in recent years, making aggressive moves over territorial claims in the South China Sea, Taiwan, Hong Kong, and in its disputes with India, Canada and Australia. It has to take a lot of the blame for this deteriorating situation.
Yet how does hardening defence ties between three of the Five Eyes improve it? The US and Australia are already in the Quad pact with Japan and India. A regional arms race is under way and other countries may seek nuclear-powered subs.
France is a neighbour with its territorial interests in the South Pacific so the sub snub is unfortunate if the aim is pressuring China. France last month took part in defence exercises with the Aukus nations, Japan and New Zealand in the South China Sea.
Australia is giving up potential soft power influence with China. And basic deterrence - short of entrenched hostility - already exists.
China has well and truly received a message from the US, European Union and its own neighbours that it needs be more cooperative internationally. The world also needs China's help on climate change, North Korea, and reducing the risk of pandemics.
The best long-term security strategy is to keep a mix of pressure and encouragement under control, rather than to escalate and ring-fence an already defensive power.
Arguably the momentum is towards continual tension that could spill into conflict.