I'd argue that it would work in any nation with an educated population where the leadership is listening to health experts and not undermining the containment effort or lying about the danger.
[0] https://www.who.int/news-room/articles-detail/updated-who-re...
[1] https://www.statnews.com/2020/01/31/as-far-right-calls-for-c...
They were able to eliminate covid in states of equivalent size as NZ, in effect achieving something just as impressive. But because the country is bigger, all it takes is a cluster in a single state to then propagate to others.
Australia is a pretty small country. In a country as big as the US it would be virtually impossible to eliminate without extreme levels of control over the population.
One of the giveaways was in their briefings at the time. New Zealand was interested in every new case, because you don't get to elimination with some sort of high level statistical approach, you get there one case at a time. Australia was happy to cheer success if it had fewer cases this week than last week - but fewer isn't elimination.
New Zealand left Level 2 only after weeks with zero new cases. Because they understood that "it's just one case" plus "infectious disease" multiplied by time = unlimited cases. Meanwhile Australians decided they were done, after all it's only a few cases, what's the harm? Well this is the harm.
As for your edit according to which this is only possible in large countries if they are totalitarian, the tactics China used are exactly the same that NZ has used, and are fully consititutional in the United States. Basically, telling people not to leave their homes for two weeks, using the Army to deliver food and supplies, and stopping travel between cities. These tactics have been implemented historically in the US in other epidemics and pandemics, so unless your claim is that the US is authoritarian, I don't follow.
Here in Canada I'm not allowed for the next 28 days to socialize with anyone outside of work. This is more restrictive than what was imposed on most cities in China.
You can also legally take them into a complex and prevent them from leaving until they test negative, as has already been done for other infactions in the US.
The executive branch in the US also has the authority to rapidly execute such measures, and has done so historically.
If New York was isolated totally and completely self governed, you have a hope of achieving what NZ achieves.
Even a country as small as Australia is evidence of this thesis. They can get it under control in one state but a cluster pops up in another and it becomes a never ending game of whack a mole. If Australia was only Sydney, covid would be a distant memory. If Australia, population of 25 million, can't eliminate it, then trying to do so in a democracy with 300 million is a pipe dream.
This includes outside gathering.
The end result is that I am not allowed to engage in any in person social activity for the next 28 days, at all. The only context in which I will be able to see people outside of my dwelling will be going to work (sadly/luckily I work remote), and getting groceries.
So basically, I'm banned from socializing for the next 28 days at minimum, and so are most people in Québec.