It's perfectly safe and the EU have no issues with it in terms of safety. In the US, they put a few more chickens in a cage than we do, so the living conditions rise from over crowded to slightly more overcrowded.
Being slightly more overcrowded can lead to slightly less sanitary conditions. In the US this is countered by washing the meat with water and a small amount of chlorine, a bit like drinking water in most of the world. The EU feel that if better living conditions were provided for the chickens, a chlorine wash would not be required. They're barred from the EU for animal welfare reasons.
I've never managed to find any statistics outlining the difference in instances of salmonella between the EU and US.