Australia certainly has room for improvement. Walk down any shopping mall or street and you’ll see grossly overweight people (“land whales”). T2 Diabetes is out of control. Drug taking and smoking are still prevalent.
As an Australian I can confirm this is true. 
As an Australian and American (and a native Kiwi) I can confirm it’s way worse in America. The raw % of population in AU vs. US that has a BMI>30 kg/m^2 isn’t that different, but the % over 40 or 50 … my observations would be way higher. The degree of lack of activity and processed food usage also worse in the US, but AU tends to follow behind the US in the bad behavioral trends … so give things another decade.
Having travelled through New Zealand, Australia and the USA over the past several weeks, I can definitely say through my observation that the USA wins the obesity award hands down. You may think Australia has an obesity problem, and it probably does, but it pales in comparison to that in the USA.
I know America wins the obesity “competition” hands down. Don’t dispute it.
I’m simply pointing out that to hold Australia up as some glowing example of how to maximise expected lifespan is probably a bit rubbery. Like I said, Australia certainly has room for improvement.
There are factors other than purely health-related measures. For example, the Australian population has effectively been disarmed, while America has a high rate of gun-related deaths. Not sure what difference that makes. A lot more than “ dangerous fauna” I’m sure!
Sharks and crocodiles kill an average of about 3 people per year…
I think all the new speed control cameras in New Zealand and Australia have increased the average lifespan there by reducing traffic fatalities.
However it may reduce lifespan due to stress and trauma from speeding tickets. 
There were 18,456 homicides in the USA in 2023.
In Australia there were 409.
USA population 343,000,000.
Australia population is 26,000,000.
It’s about 3X as much in the USA per Capita.
We have had 2 coworkers shot in Indianapolis (one is deceased and the other on life support right now) in the last week. It’s just getting way out of hand here.
Since you brought it up, guess what else the USA has way more of than Australia:
https://x.com/Scientific_Bird/status/1823429633091735565
Edit: And as somebody said, ‘Asians are the X axis.’