Yeah I know it's tongue in cheek, but the mocking should really go the other way, haha. Look at our washed American eggs that scare the Europeans who are used to two orders of magnitude higher incidences of salmonella:
"Overall, egg contamination from industrial systems has been reported to be 0.005% in the United States, 0.37% in Europe, and between 0.5% and 5.6% in China"
That's not the number you're looking for with "industrial systems" they mean keeping hens in batteries and that's outlawed in the EU, has been since 2012 (though the actual phase-out took longer). So you're probably looking at maybe Serbian, Belorussian, and Albanian stats.
Overall the study you've cited is not the right one to look at as they're comparing different methods of keeping chickens, it's not focussed on hashing out regional differences much less the wash vs. don't wash issue.
Fair enough (it was actually way more countries, because I found that the study they quoted quoted a study, so it included Spain, Portugal, others except the UK and Nordic countries), though the study I linked to actually found 2 cases in the "alternative" keeping of hens compared to zero in battery cages. Wasn't statistically significant, but still the point is the washing and refrigeration of eggs greatly lowers the chance of salmonella risk. Animal welfare is sort of a separate issue, though at least it's getting addressed in the EU.
It's just not big enough of an issue to mandate universal vaccinating: Any salmonella are generally on the shell, not actually infecting the egg. At least in Germany only flocks >350 animals need to be vaccinated.
Also it has to be said that European cuisine is actually quite risky when it comes to salmonella: Proper Tiramisu uses raw egg yolk, proper mousse au chocolat raw egg whites, and a carbonara might contain both semi-raw (depending on how you like it). But it's also well-known that you use fresh eggs for those as the fresher the eggs the less bacteria there will be on there even if infected and it's not like people keel over from a single bacterium. Also don't feed those dishes to small kids or the elderly.
German press reports that authorities say that bacteria loads (not just salmonella) are pretty much similar comparing conventional (that's barn and free range) vs. organic (free range deluxe) eggs (9 vs. 6 vs. 4 hens per m2), with a nod towards organic eggs as those don't come with bacteria resistant to antibiotics.