I think I've stated elsewhere that I suspect a lot of the big and predominantly Black crime wave of 1960-1994ish was caused by childhood inhalation of leaded gas fumes, a problem that persists in a weaker form because of the continuing soil contamination of some areas that causes the inhaleable lead to rise again as dust in the summer months.
In that case, the outlawing of leaded gas in the medium term led to a reduction of violent crime.
That would technically qualify as government intervention fixing it and it is neither a genetic nor a cultural factor.
Here's a simple example of why I find it hard to take the culture argument seriously. I seem to recall barbos is a Russian expatriate from the old board (apologies if I am mistaken). Russia has never had a well functioning Democracy, so much so that some believe there is a "cultural tendency" towards towards autocratic government among Russians. The evidence for this hypothesis is as good as "North American Blacks have criminal tendencies." Would you be inclined to accept that judgement, barbos, or would you argue instead that Russia has been afflicted with a series of negative circumstances that has led to sequential autocracies?
Except culture is shaped by chronic long-term environmental conditions, usually in ways that allow the people to tolerate, cope with, justify, and even celebrate, and (in the case of Russia) have nationalistic pride in those conditions. Thus, even if larger circumstance have pushed Russia toward autocracy and away from democracy, the odds are extremely high that Russian culture would have adapted to that context in a way to embrace autocracy and devalue democracy, which in turn would dispose the Russian people toward less democracy and more autocracy in the future. IOW, without a very conscious and deliberate effort to break the cycle, environment shapes culture in ways that lead culture to reinforce that environment and so on, in a feedback loop.
The Russian people are not unaware that they live in an undemocratic democracy under a megalomaniac. Valuing democracy would force them to view Russian society as clearly inferior to most nations of the West. Putin rampantly murders and destroys the lives of the few in Russia who criticizes him, and does so out in the open. Even very rich and recently powerful people, including editors of once dominant new outlets have been stripped of most their wealth and live largely in hiding. The people know this and yet they do more than just sit quietly by hoping for an end to his reign. By most accounts I have seen, a large % if not majority worship Putin and his machismo, and seem more proud of the Russian "strength" they think he is displaying to the world than the near genocidal threat he poses to their own people.
All you have to do is take Putin and his actions and pluck him from Russia and put him in the White House. Would you imagine that the American people would react differently to him than the Russian people? If so, any such difference is a difference in culture.
Oh, almost forgot, I think the same thing applies to American Blacks. Even if environmental circumstances (e.g., poverty) are a major factor in crime levels among blacks, the longstanding prevalence of crime among blacks would almost certainly have a cultural impact combined with the impact of long-standing government sponsored and blatant injustice against their communities. Every relevant established principle within sociology and psychology would predict that this would shape culture and likely in ways that devalue the legal system (trust in it and respect for it) and view being prosecuted and incarcerated by it as less shameful and "par for the course". All of this would tend to increase the odds that a person within those communities would be willing to commit a criminal act, which in turn shapes the culture more, and so on.
