From what I can see from an EU perspective: The training you get to become an officer in the US seems to vary a lot between places. That explains lot of differences.
Also it’s quite short IMO. Here in Germany it takes 2 1/2 years to become a policeman, 6 Months of these as a trainee. And still we have a number of problems.
https://xkcd.com/37/ oh wow, I need some mind-bleach now.