What does that have to do with neoliberalism? Also, you'll have to say which presidents you see as being responsible. Wikipedia says Trump was neoliberal, I've seen it applied to other presidents. Trump was impactful on the world because he was so ineffectual in general. But I think every president in living memory wanted to reduce drug use and the supply of drugs coming into the us. In a free society it's hard to stop people from doing what they want, even if they take drugs that hurt them, kill them, or might not do anything bad (like pot), large numbers of people can supply enough demand to overcome the impact of law enforcement.
Of course fentanyl is a society destroying thing, the impact of that and things like heroin lead to me not knowing what to do personally to stop this. Media reports claim fentanyl components are coming from China. So now what?