To what extent do nonstate actors exert independent influence on international relations?

To what extent do nonstate actors exert independent influence on international relations?
The influence of independent actors on international relations can vary from nothing at all to something outside calculation. Plenty of people acting independently, working as individuals and as groups, do things on a daily basis that have no effect whatsoever on international relations. But in the case of the extremists who plotted and executed the acts of 9-11, they catalyzed monumental changes in international relations and policy, and could fairly be said to have changed the course of history.Certainly there are many other groups or organizations whose actions fall somewhere between these extremes. The Red Cross, Peace Corps, Doctors Without Borders, and other such groups are but some of a countless number of organizations that could be cited as being "nonstate actors" having a variable effect on international relations. The broad variation in the acts of independent operators can have widely varying effects on international relations.