Not to be blunt, but police training in the US is just unacceptable when looking at the standard of officer they produce. And the fitness situation of those officers is regularly alarming.
Training requirements in the US are often far less extensive than required in many EU nations. And yet, recruiting people to LE is difficult as it is. If training/education requirements were higher many departments would have to pay more and have a smaller number of cops, which is often deemed unacceptable or politically "soft on crime".
In the police department itself, speaking from experience, there's a major attitude problem. A sense of group identity as distinct from the public, press, politicians and etc, the "thin blue line" between order and barbarism; a "nobody knows the trouble I seen" martyrdom and elitism, combined with military mindset and the result is things I was told as a cop:
Never criticize a fellow officers conduct if you were not on-scene, especially not outside the department. Never criticize a fellow officers' conduct outside the department PERIOD.
"You need to harden up," I was told once by an older cop, "you
care too much. You're gonna burn out." (I did, but I'd rather care and burn out that become cold and indifferent to human suffering).
There was also a standing joke, during yearly PT (physical testing) that we never saw some of the hugely fat Sgt's and LTs out there running the course.... it was understood their paperwork was falsified.
I had to rewrite a lot of incident reports that my Sgt or LT found unacceptably honest.
These are some of the reasons police reform is an uphill battle in the US.