China’s rising military and economic forces prove too powerful regionally by the time Trump (or an isolationist like him) ends the Presidential term in February 2025.
China has sound economic improvement and regime survival reasons for its evolution south.
The US will place continuity of trade with China above military confrontation with China.
By the late 2020s the US will have withdrawn its 4 services (Army, Navy, Marines, Airforce) based in East Asia to Guam, Hawaii and the continental US.
The US may well decide to maintain its monopoly of the most advanced nuclear propulsion and weapons technology in the Indo-Pacific. This is partly to retain primacy over its Western allies (eg. Australia, Canda, Japan, South Korea and Singapore). The US also wishes to avoid passing advanced propulsion and weapon secrets to these allies as these allies may fall and pass the secrets to China. The F-22 is a conventional case in point.
China by the late 2020s, having consolidated its control of the South China Sea will continue the process of neutralizing/Finlandizing the countries of Southeast Asia (including the Indonesian arc over Australia's northwest). China will also indebt/Finlandize East Timor, Melanesia (eg. Papua New Guinea, the Solomons) east to the Cook Islands and southeast to New Zealand.
Australia feels all these pressures and becomes more nervous.