If the US police have this problem and other (wealthy democratic) countries don't – or even if comparable countries have the problem too, just not quite as bad as the US has it – what makes US police different?
Racism and racial inequality. Yes, that's very real, but don't think for a moment other countries don't have that problem too – they do. But yes, historically speaking, the US was very much an outlier of extreme racism – few other countries ever had anything comparable to "Jim Crow laws", and the most obvious comparators (apartheid in South Africa and the Nuremberg Laws in Nazi Germany) are not what the US really wants to be compared to. On the other hand, my personal impression is that contemporary Americans are (on average) actually much more highly committed to anti-racism than people in most other countries are.
Could there be other relevant factors causing problems unique to US police? I think, everyone is (quite rightly) focused on the racial inequality issue, but could there be other causes which might be less deeply entrenched and quicker to fix? Easy short-term wins?
(My thought: US has more independent law enforcement agencies than any other country on earth – force all the smaller ones to merge – bigger police forces tend to have a more professional culture, and a smaller number of big police forces is easier for the media/NGOs/etc to hold to account than a larger number of small ones.)
And I’m not suggesting the US should have one police force for whole country, or that EU should take over policing for its member states. In a federal system like the US, local policing is a state government responsibility. So I wouldn’t advocate going any further than merging local police into state police. And in bigger states, like California and Texas, even that is probably going too far-but one could at least merge city police forces into the county level.
If you really want to feel sick read-up on the Highway of Tears and the systematic brutalization of indigenous women by Canadian society.
On that topic, how do US law enforcement treat Native Americans? In the present debate there seems to be very little attention to that question.