Earlier quoted context omitted.
Seems to me like the real motivation is defending their own agricultural industry. American chicken is cheaper and likely just as good. The health claims are weak, everyone can understand protectionism, but it is often masked behind other claimed goals. The data on salmonella is not super solid, but points to higher levels in the U.S. https://www.bbc.com/news/uk-47440562
Having lived in Europe (UK, France) and North America (Canada) I can assure you that American chicken is not just as good. It's not just chicken. All sorts of meats are worse in quality.
Well not really, especially when it comes to Beef. Pork has has a rather diverse selection from both side, but generally I think they are about the same.