Art-History -- Can we separate the Art from the History?

I have just been reading an interesting set of remembrances from Richard Press.  One of the most compelling to me was a memory of Robert Frost coming into his father's store in the 50's to have some new Donegal Tweed jackets made up.  Some googling aimed at an image of Frost so attired brought me to the website of the mass-market screen-printer, Zazzle; to this shirt, specifically. I imagine that Robert Frost would be mortified by the association of a line of his poetry with a grown man in a tee shirt, and all the more upset by the fact that his line was printed on the shirt.

Robbie and his Donegal three-piece are very upset right now.

It's funny to me how fragmented bits of culture, like a poem or painting here or there, can move down from generation to generation, leaving other aspects of the zeitgeist that spawned them behind.  This leaves me wondering: does any study of art or literary or cultural history really create a valid picture of its subject without including a wide-reaching social history of its times?  Press recalls Frost's brown, bespeckled tweeds as something not unlike "the stones in the walls of his poems".  Can we really process "Mending Wall" in toto without some sense of man, jacket and cloth?  What jackets do the wall-walkers in today's readers' minds wear?  Does this color contemporary readings of the poem?
Can we, as another example, understand "Guernica" without parallel readings of Homage to Catalonia, and For Whom the Bell Tolls, and a lecture on the Condor Legion and German non-interventionism?  Of course we can still appreciate it; "Guernica", like "Mending Wall", like any good piece of art, affects us in ways unrelated to time, to era, to contemporary movement or style.  Analysis, however, may require a little more than a phenomenal understanding.