I'm not saying we shouldn't bother removing the bad apples - they absolutely should be weeded out. That only solves part of the problem, as even good cops get caught up in situations where it's impossible to come out looking good. The more we can minimize the number of antagonistic and confrontational interactions between the police and the public, the better it is for all involved.
You are correct when you say there are variations amongst countries leading to differing incarceration rates. However, that doesn't explain the extreme outlying position the US finds itself in - the highest rate on the planet. And, when compared to other developed countries - not just Canada - by a long shot. That has more to do with policy than criminal activity.
You mentioned poverty - that's one of the social conditions I'm talking about.
Rehabilitation, street cred, prison rape...there's nothing unique about the US in that regard. It's simply the sheer numbers involved.
Several years ago, our then-Conservative government started yammering on about getting tough on crime. Even the Texas (Texas!?) government advised them not to go down that road.