I think if this website does a good job of just being itself -- and then does something to advertise its presence to European XC skiers -- some European skiers will join for the reasons J Klok gives -- partly to get a chance to practice their English (an important career skill), and sometimes because they lived in USA or Canada for a while, and they like to feel they're staying in contact with that experience.I hope this will be allowed to become Global rather than just American. Europe totally lacks a general website, each language gets it's own, and therefor forums stay small. Most of Europe speaks English though, as a common language.
Another thing to try is add some specific Forums which are especially interesting to European skiers, but also to some North Americans:
* World Cup racing
is one that immediately comes to mind, from looking at the history of rec.skiing.nordic and seeing what participants with European-sounding email addresses or names tend to post about there. (I confess I also like the idea of trying to keep the racing "spectators" from clogging up the discussions among actual race participants.)
A more "long-shot" attempt at a Forum topic might be something like "Theory of Technique", based on the stereotype that Americans are more likely to want some specific tip for "what works for me now" -- while skiers who went thru European or other non-USA education systems are more likely to think there should be wider-ranging theoretical principles to examine (? and more likely have actually learned enough hard science and mathematics in their education to have a chance of understanding the theory?). Only a stereotype.