What did Australia do that was different? First was a hard lockdown starting in January 2020, not March as in the US. Second, the lockdown limited how far people could travel from their home and the amount of time they could be out of home each day — 3 miles and 1 hour. Third was aggressive contact tracing. People use QR codes on cell phones to sign into stores, restaurants and recreation sites that they visit so tracers will know who has been exposed to the virus.
The end result is that Australia is mostly back to normal, masks are optional and there are no lockdowns at present nationwide. Sporting events are open to full capacity. Movie theaters are open, although they still use empty seats to separate patrons.
Conversely, the US is still struggling.
New Zealand acted in concert with Australia, with even better results.