I can see why this would be a difficult topic to find sources for. It is easy to google a straightforward topic, but this topic is tough to explain, and tough to find key words for.
How about if you search for this:
The influence of literature upon society
I found a few good sources that way. Also, I use questia.com. MAybe that will help you, but you have to pay a little $$ for membership.
ALSO, this topic is too broad. Choose a society or a particular aspect of a society. Also, you might want to choose particular kinds of literature or particular kinds of influence. For example, you might want to write about the influence of literature on the gender equality/inequality in the 18th, 19th, and 20th century.