This is Ba Sing Se levels of delusion for some people.
In fact, there are plenty of commentators downthread who don't see it as a mistake either. Years of demonisation and propaganda has gone into supporting the belief that as soon as somebody steps out of line it's necessary to beat them back into line, or shoot them if they do not comply. It's no more a mistake than the millions of people in US prisons: it's policy.
US police forces seem to have a very short training which, as far as I understand is not centrally vetted by any federal organism? And considering the short training time it seems to be mostly focused on tactical and firearm training.
Compare that with European forces and you see a completely different reality. In Europe the police is generally seen as peace-keepers, force is absolutely a last resort (probably not so true for crowd control units but certainly true for daily policing).
Correct; some states have laws mandating training hours for barbers that are longer than that mandated for police [0].
> not centrally vetted by any federal organism
As with many things in the US, these rules are mostly state-based (read: 50 different, often overlapping but also often contradictory systems) but with a patchwork of federal oversight.
For example, in 2012, the federal government stepped in with a judicial document called a "consent decree" aimed at reforming the Seattle police department after "a pattern or practice of excessive force that violates the U.S. Constitution and federal law" [1].
That's an example of federal oversight, but it only happens after problems have already occurred; it only applies to the city of Seattle; and it's temporary. Only a month ago [2] the city was in court petitioning for "we're all better now, federal oversight can end".
After saying in court they were reformed and would no longer use excessive force, Seattle PD used so much tear gas in a residential neighborhood that it seeped into peoples' homes [3]. Then they announced a 30 day ban on use of tear gas [4]. Then about 48 hours later they used tear gas anyway (after using "blast balls" containing "pepper spray gas" the previous night and insisting it didn't count as tear gas). Finally a federal judge stepped in [5] and issued a 14 day ban on its use - another example of our federal oversight being reactive and not proactive.
Oh, and did I mention Seattle PD shot a "less-lethal" grenade round directly at a protester, causing enough blunt force trauma to stop her heart and require life-saving CPR? [6] That was on the same night they used tear gas after promising not to.
And they threw flashbang grenades at the medics who were trying to save her life. [7]
(in case it's not obvious, I'm a Seattle resident and I'm pissed)
Another example of how complicated our justice system can be that might surprise people from other countries is all the levels of police forces we have - city police / county sheriff / state police (plus federal law enforcement - FBI, TSA, border patrol, and so on). Especially in rural areas the county sheriff often wields a tremendous amount of power [8].
0: https://www.cnn.com/2016/09/28/us/jobs-training-police-trnd/...
1: http://www.seattlemonitor.com/overview
2: https://spdblotter.seattle.gov/2020/05/08/city-of-seattle-fi...
3: https://www.thestranger.com/slog/2020/06/04/43840246/seattle...
4: https://crosscut.com/2020/06/seattle-issues-30-day-ban-tear-...
5: https://www.kuow.org/stories/federal-judge-in-seattle-bans-u...
6: https://www.kuow.org/stories/this-26-year-old-died-three-tim...
7: https://www.reddit.com/r/Seattle/comments/gywxhz/folks_i_nee...
8: https://theappeal.org/the-power-of-sheriffs-an-explainer/
states run themselves, and the federal judiciary basically only steps in when state/local governments don't follow their own rules (the presumed expression of the will of the people) or violate the constitution. the constrained executive response follows from the judiciary (and sometimes the legislature).
and that's the way it should be. you want power local and limited, not consolidated and far away. that would only make things like use of force worse.
so the immediate appeal to authority should be to the local, and then state, judiciary and legislature stepping in with corrective actions. the feds aren't of much use here. they're intentionally a line of last (and slow) resort.
it's worse if we had the same sordid problems at a state or national level. it's rolling the dice once or 50 times vs. rolling them ~50,000 times.