I had the same problem. I think it's something on google's part. If you applied through hubpages the URL would have been automatic and they wouldn't have asked you for it.To be honest, I got frustrated and applied to google adsense through a different website called wizzley because I just had too many problems doing it through hubpages.
There's definitely a problem but its not getting fixed on either part.
Hope I answered your question a little bit.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.