Australia had 923 COVID deaths total, for a population of 25 million. That’s 36 cases per million.
For comparison, the US has 1,887 deaths per million. Most European states aren’t much better, or even worse, per capita.
Now, you can argue if these extremes are worth it, or not, but it seems clear that what they are doing is saving lives.
Australia quarantines internally, which is comparable, if not more difficult, than countries that close their international borders. Imagine if LA was quarantined from the rest of California. That's the closest analogy I can make to the subject of this thread.
And yes Australia is a large island but if you take the briefest glance at a population density map, you'll see that the vast majority of the population is concentrated in a few coastal regions and particularly around Sydney and Melbourne.
Lockdowns are not 100% effective, but just an attempt to slow down the transmission rate. Think of it as a type of defense-in-depth. Australia (and New Zealand's) true advantage is their natural isolation from the rest of the world and their ability to control/track who is coming into the country.
Arguably the US would have it easier to control, since half its population is in low density rural and suburban environments that significantly reduce social contact.
(Would be good if someone had a calendar recording this)
australia's use of a few lockdowns and draconian border resitrictions eliminated covid within the country and meant there's been little restrictions for anyone for most of the pandemic.