Out of every other modern Nation, why is it that US has such extreme police brutality (bullying)? Is the #1 reason that there aren’t balance and checks for pow

Out of every other modern Nation, why is it that US has such extreme police brutality (bullying)? Is the #1 reason that there aren’t balance and checks for power? I.e there isn’t effective policing of the police? When was the last time a police officer was put in prison for stepping out of line?