It can be deduced that Whitman wanted to express that:
A metaphor is typically used to make comparison between two things. In this case, Whitman compares America to a group of people singing like a choir.
It simply means that each individual of the country doing their part is what forms the nation. It means that everyone plays a vital role in making the nation great.
Learn more about metaphor on:
https://brainly.com/question/9418370
