[shoo]

another factor could be how cohesive / fragmented the government response is -- maybe this is another facet of "authoritative control".

here's a crude model as a straw-man thought experiment:

australia has a federal government with some degree of control but the 8 local state/territory governments still get a reasonable amount of ability to make local decisions. The states often disagree with the federal government, and with each other, and have disagreed about the appropriate responses to covid in many cases.

Suppose the federal government has no ability to control anything. Each local government has a 95% chance of doing something reasonable in response to a pandemic and a 5% chance of doing something stupid. If we make the poor working assumption that each local government decides what to do independently of the others, then about 2/3rds of the time we would expect all 8 australian local governments to do something reasonable, and 1/3 of the time one or more local government will respond to the pandemic in a stupid way. So maybe we got to see the 2/3rds outcome in australia -- or perhaps we actually saw a 1/3rd outcome where stupid decisions were made that dramatically elevated risk, but we simply got lucky.

In contrast the US has say 51 local government regions, so there's about a 7% chance that they all do something reasonable and a 93% chance that at least one local government region does something stupid.

Then if it is hard or impossible to isolate the impacts of bad decisions to each local region, the impact of poor decisions in one region can help outbreaks spread in connected regions.

On another hand, a downside of having a strong central control of the entire country's response is that if that central response is stupid, then the entire country starts cohesively doing something stupid, whereas a country with more fragmented/decentralised decision making might fare a bit better locally.

[vmception]

that's a very interesting way of looking at it, but also in the US you would have very many people in a place with reasonable policies implemented that will simply go to a place with unreasonable policies

(assuming reasonable means policies that mitigate and slow down the spread of COVID19, but I'm not saying anybody else reading this has to subscribe to that thought or the idea that COVID19 is worthwhile to slow down)