Why the difference in death rates from covid 19

[beez]

I was looking through the stats for cv19 and for the life of me i cant work out why the discrepancy in death rates around the world , especially amongst the 5 eyes nations . First up the world average sits at 3.76% which is a vast improvement over earlier day . 
now for 5 eye nations .
Australia = 1.28%
Canada = 7.57%
New Zealand = 1.4%
United Kingdom = 15.04%
United States = 3.27% 
I would have thought our hospital systems to be roughly on par , certainly our medium ages are sort of close going from 38-42 . Life expectancy was between 79 and 83 years old so overall no huge discrepancies . Reporting criteria maybe ? . Scratching my head here a little , any ideas .
Thoughts RN3 .
source for cv
Life expectancy
Medium age

There is no accurate death rate because in order to determine death rate, you have to know the known number of people who have had Covid.

Many scientists speculate that the death rate is much lower because initial studies indicate that as many as 10X to 20X people have been infected with no symptoms.