Harsh policing would not change culture, even if it was done fairly, in the interest of community welfare. But U.S. policing is far from fair: U.S. police instill fear, rather than respect in the public, even in many moderately well-off areas that are free of street gangs. Legal and regulated prostitution, a definitive end to the drug war, would allow us to significantly defund the police, and pour those into efforts that could actually help. Moreover, this would decimate the revenue streams of many street gangs, which immediately reduces their "coolness factor".
There is some concern that most of the money freed up by this could end up poured into efforts that have a track record of not working. Alas, I think this is fairly likely, but it's no big loss: currently, all of that same money is being poured into different efforts that still definitely do not work. And if we get lucky, a fraction of the money may actually go to efforts that actually have a positive impact on cultural problems.
Here's some reading on them in Russia: https://www.londonmet.ac.uk/news/articles/svetlana-stephenso...
I'm going to challenge you to find a citation to back up this belief before you continue going through life believing it, because it's a dangerous one, rooted in ignorance, that causes racism.
People like blaming it on poverty and lack of education funding and all kinds of other things. Yet compare former Soviet countries to the US. All of them spend less on education than the US does. Their populations are likely poorer than even the poor in the US. Their quality of life is lower, however, gangs aren't as big of an issue because they're not allowed to fester. The culture doesn't view gangs as something to aspire to. Being part of a gang isn't seen as "cool" by large groups of people nor is failing in education.
I do agree that a lack of education and subsequent opportunities is a large part of the problem, but it's probably not a lack of education funding that's causing it. Learning simply isn't considered "cool" by a lot of people. This puts them on a path with few opportunities, which leads to their kids having fewer opportunities.
What makes all of this even worse is that prisons in the US are breeding grounds for gangs. As long as things like that remain a part of society you won't be getting rid of gangs no matter how much money you throw at education.