From my point of view they are completely autonomous organizations. There are contacts between European bosses however. Dutch and German Hells Angels are often to be found on the same events, probably because the Netherlands and Germany are the two countries with the strongest -not to forget the most criminally active- Hells Angels membership. Eventhough a lot of strong German Hells Angels chapters have been banned ( Frankfurt, Kiel, Berlin,...).

But don't they have an international chapter president, like Taco Bowman for the Outlaws?

No, they do have a national chapter president however. In Germany it was Frank Hanebuth, while Daniel Uneputty was the Dutch chapter president.