Question

How does the repetition of the word singing influence the overall meaning of the poem “I Hear America Singing” by Walt Whitman?

Answer 1

The repetition of the work "singing" is associated with the enumeration of who is singing: for example the carpenter, the mason and the shoemaker. 
Therefore, "singing" contributes to the feeling that everyone is singing: it  provides a feeling of unity. 
This singing also symbolizes hope for well-being: all those singing people have a job and a secure existence. 
The correct answer is: The repetition emphasizes hope and a unified vision for America.