US customers have more spending power than the average EU customer. So the ads are worth more as there's more opportunity to sell.

GDP with PPP compensated is on par or better in NW Europe and for all of the EU it's about 70% of the USA (which has about 100m more people than the USA). You'd expect it to be a lot closer.

Yes it is most likely to be less but not a factor of 3 simply based on purchasing power alone.

I'm sure it's not the only factor but it's surely one. Here in Spain we really make a lot less than in NW Europe. central and eastern Europe are even worse off.

What is NW Europe?

Do you mean US advertisers are paying three times more to FB than the advertisers in the EU?

Please don't confuse things. FB users aren't FB's customers. FB doesn't get any money directly from the (on average just a little bit) richer US users.

The US also has close to no data privacy protection, so you can also practice whatever targeting and manipulative nonsense you want on your subjects.

The delta there shows what that's worth.

And generally no consumer protection, so you can milk the marks out of more money than you can in Europe.

"Shockingly little revenue targeted ads generate per user" is also relative to the context. I bang on these numbers a lot on HN because for many of us here, the amount of damage Facebook does to our lives, the amount of ads it shoves in our face, and the way it has contorted an entire industry into surveillance capitalism, is way, way more than $20/month worth of damage to our lives, culture, and society. It is also a good way to counter the frequently-proposed "what if the companies share ad revenue with their users?", which along with being sort of a "pull yourself up by your own bootstraps" problem if you really analyze what that entails, has the even more fatal problem that there really isn't any money to do that with. If we cut you in for 50% of the ads you see in a month, you might be looking at a whopping $15-20 a month, or, pretty close to a single hour at what is roughly the de facto minimum wage. Even if we ignore how that instantly pushes all these companies from megaprofitable behemoths to bleeding money out of every orifice, $15-20/month isn't enough to make a compelling story on that front.

I think a lot of people have a mental model based on the size of these companies that they must be making hundreds of dollars a month per user, and it's good to run the numbers to show they don't so society can make more reasonable plans.

Europe has stronger privacy laws.

I'd guess it's a combination of three things: GDPR reducing the effectiveness of targeted ads, the online advertising industry being more mature/established in the US, and Europe being generally more fragmented, reducing the size of ad campaigns.

Europeans are less likely to fall for ads.

People are on average the same everywhere, I think.

Culture may differ, but human brains work the same in the end.