The protective barrier is true, but you’re either making assumptions about the rest or you’ve been misinformed. There really aren’t major issues in any of the developed countries today, but the washing and refrigeration is still the safest with the longest shelf life. It isn’t the condition the chickens are kept in - there are countries where it’s much, much worse than in the US - it’s just that chickens very easily carry salmonella.

Many years ago, more countries washed, but there were some escapes, especially one from Australia with the eggs exported to the UK, and it got a bad name, so some countries dropped it, but the US figured out how to make it work consistently. Most countries require chickens to be vaccinated, but the US hasn’t needed to because of the washing and refrigeration.

Lots of good info online. Here’s a USDA article on it, and here’s a higher level NPR piece.