All of the hired girls in My Antonia were immigrants or their parents were. Language and culture barriers created conditions that were particularly bad for immigrants. Immigrants during WW1 had to deal with similar hardships,they left trying to escape the war, yet are pulled back into the fire in America. Cather, clearly wants to shine a light on the sacrifices which many immigrant families have made.
In My Antonia it is imagery. Willa Cather sets the mood with Jim Burden, by having him tell what happens in the