What is the theme of I hear America singing ?

The dominant theme of the poem “I Hear America Singing” is work, specifically hard and intense manual labor. Whitman clearly dedicates the poem to people who work hard day by day: mechanics, carpenters, masons, boatmen, deckhands, shoemakers, hatters, wood-cutters, ploughboys, mothers, wives or girls.

it foreshadows the theme of the paragraph and hints the topic that will be discussed in the paragraph!

"germany's geographic location was an advantage when it was on the offensive in the war because it was situated next to an extremely wide river, the rhine, which was difficult for the allies to cross."