Thomas Greven is an adjunct professor of political science at the Freie Universität in Berlin and coeditor of the book "Globalisierter Rechtsextremismus? Die extremistische Rechte in der Ära der Globalisierung" (Globalized Right-Wing Extremism? The Extreme Right in the Era of Globalization).

DW: Links between US and German far-right extremists and neo-Nazis go way back. I gather that one of the high points, if you want to put it that way, was David Duke coming to Germany in 1976, when he was the "grand master" of the Ku Klux Klan, and calling for Hitler's regime to be rehabilitated.

Thomas Greven: I think the high point of collaboration was not Duke. It was the relationship between the National Alliance in the US and the NPD in Germany [especially in the 1990s - ed.]; both were kind of vanguard parties and they actually had a little bit of an infrastructure, exchange and visits. But this was more symbolic than anything else. It's not like American neo-Nazis or Klan people or the militia movement look to Germany, either for the historical experience or for any kind of real inspiration or input.

In the US, they have freedom of speech, so the far-right extremists can use the symbolism [Displaying Nazi symbols is essentially banned in Germany - ed.] and it's a provocation. And so they tie their ideology into this historical experience, but not in any real way in the form of cooperation. That was never really the case. I think that collaboration is not about substance. It's more about lifting each other up symbolically.

When you look at it in terms of politics or policy, there's a distinct difference there also. The German right-wing extremist actors were a little more serious when it came to actually formulating policy.

Read more: Charlottesville violence reflects Trump America

The American movement is less serious politically - there's white supremacy for sure, but they don't have any policy ideas on anything else, like trade policy. They don't take a cue from the more serious ideological and programmatic underpinning of the German neo-Nazi party, either historically or presently. At the same time, the US movement is more violent. There's a lot more connection to crime. They are armed to the teeth - that's not the case in Germany. And there are some health issues: You have more people who are bordering on the insane. They have mental health problems. That seems to be much more the case in the US than in Germany.

So when it comes to contact between US and German far-right extremists, there is some sort of networking: They lift each other up. They're moral support for each other. On the internet there will be chat rooms where they're exchanging information. Merchandise seems to be one issue where there is cooperation.

Read more: Merkel decries Charlottesville violence as 'disgusting'

In the US you have the advantage of freedom of speech, so a lot of European actors use the US to host things on the internet. The commercial aspect is not to be underestimated: Music and paraphernalia are exchanged on the internet. It's a business.

But when it comes to information exchange, it's not really substantial in terms of ideological fine points or programmatic messaging. And certainly the rank and file don't communicate with each other, because there's a language barrier. They are not able to communicate. In Europe they have tried working with each other, but then they're nationalists, and they have a history between countries or between ethnicities so that they don't get along for long; the collaboration falls apart again very, very soon.

Do you think that what we've seen now in Charlottesville, the upswing in the so-called alt-right in the US and the growth of far-right extremist groups, will have any kind of effect in Germany on the parallel groups that are active here?

With a violent event like this, I think there will be people on the fringe, the extreme, who will be inspired. They would say: "It's time that we do stuff like this. It's time that we also are more visible." But the laws are against them. In the US, as you see from the footage, there people are running around with guns - that would not so easily be possible anywhere in Europe. There are some legal limits to what they can do. But for the extremists, for the ones ready to use violence, Charlottesville will be some sort of inspiration.