Cops in the USA, as well as being scum, are terrified. The population has almost no access to mental health care, near unlimited access to guns, and many reasons to not trust the police. The police are also trained as "warriors" instead of guardians with a us vs them mentality. I'd imagine besides the legal ramifications, Uk and Eu police are just not as scared shitless and therefore don't start popping off when an acorn hits their car or a 13 year old has a stick.