Differences by country and culture - the reason why are the interesting questions.
> these need to be normalized with a population-wide sample.
Need to be?
The US (for example) has a large population ( ~360 mill ) with a poor system of government and an excess of hold over odd little religious groups (and home grown product like Mormons, etc).
Other countries have smaller populations (eg 25 million here), better more responsive system of government with better oversight, better education, better health, etc.
I see no benefit in being blended in with a bloated mass of objectively worse and dragged down to US levels.
Differences by country and culture - the reason why are the interesting questions.
> these need to be normalized with a population-wide sample.
Need to be?
The US (for example) has a large population ( ~360 mill ) with a poor system of government and an excess of hold over odd little religious groups (and home grown product like Mormons, etc).
Other countries have smaller populations (eg 25 million here), better more responsive system of government with better oversight, better education, better health, etc.
I see no benefit in being blended in with a bloated mass of objectively worse and dragged down to US levels.