Explain the degree to which you think it's possible for a literary writing to both represent a specific culture or nationality and also simultaneously suggest a shared human condition?

Yikes, this would take a good sized book to properly answer. In the case of "Of Mice and Men", certainly Steinbeck drives the factors that you mention primarily through character and setting. A killed author like Steinbeck is able to say so much with so little. It is a minimalist writing approach which makes Steinbeck's books so evocative about those points you mentioned above.

I agree with you Aslan