I think most media made in the 1990s and later have fallen into this capitalist black hole of culture.

Our governments have given corporations total control over who is allowed to access what media, and these companies have 100% incentive profit from artificial scarcity over that tiny span of time when people have interest in buying it, while having 0% incentive to preserve that media in archives meant to survive centuries or even mere decades. Most TV shows, film, music, even photos, and especially video games, that were created during our lifetimes will also disappear forever during our lifetimes. It is kind of an unprecedented situation. Never in history has such a large and productive society left behind so little of our culture for future historians to discover about us. Basically we are leaving behind our garbage and pollution, and no sign of our art or culture.

Every so often I hear a news story about some guy discovering a box of old records in his basement for music that had previously been thought lost to history. Every time I hear about that, I have to wonder what, if anything, will the future humans discover about us now that it is all digital and streaming on demand?

I wouldn't worry too much about that. The most reactionary people in the US, those who think socialism is communism and horrible labor laws are "freedom," are too heavily indoctrinated into their own little death cult. They honestly believe there is no country more free than the US and are genuinely fearful of the idea of living anywhere else, they would never move to Europe.

People who live in reality, on the other hand, see how horrible it has become in the US and are looking for a real "land of opportunity," where you do not have to be a willing slave to capital in order to have the right to the basic necessities of life. They are fully disillusioned with the "American dream," and so are more open-minded toward socialism, and are more willing to agree that maybe most countries in Europe provide them with real, actual freedom far more that what they have living in the US.

This has been my experience with immigrants from the US, anyways (and, full disclosure, I am an immigrant as well, just not in Europe).

"N has a history of mental health issues and was in a deeply abusive relationship for a few years which cause him a lot of grief."

Choosing to genuinely believe in superstitions seems to be a common coping tactic for people who have experienced extreme mental distress. It is not your place to try and "heal" them, they are probably in the process of healing themselves. That is what therapists are for, to help them heal themselves. So it is great that your friend is in therapy, it looks like they are on top of things for now.

"believing in witchcraft does not make it real it wasn't healthy to believe otherwise"

But this is not necessarily unhealthy though. It can be unhealthy for some people, but not everyone. It is really a case-by-case kind of thing, and it was a little presumptuous of you to say that, which is probably why they got upset with you. For some people, tempered belief in superstition might be a natural part of their healing process.

Of course, things can still go bad, but you can keep an eye out for any behavior that might be harmful toward themselves or others without being rude. If they do (not believe, but actually do) things you think might be harmful, speak up and address that specific behavior, not their beliefs.

And, being another person to hang out with outside of their new circle of witchcraft friends could help keep them grounded, as long as you have things to do that you both find fun together that are not related to witchcraft.

If I were in your place, I would be honest that I don't find witchcraft to be interesting or helpful for me personally, but but I feel happy for them that their spiritual journey seems to be helpful for them, and that their well-being is the most important thing for me.

Be honest and supportive, keep trying to have fun as friends together.