Actually if you've read Catch 22 this question does make sense - although it should be "who is Spain?" It's a nonsense question asked by Yossarian to show his madness - along with "Why is Hitler? When is right?" Of course, there is no answer.
sky and harry,
having read catch 22 you would realise that in his madness yossarian says "who is spain?" so to avoid plagurism the question remains "why is spain?"