How did Hughes' racial identity shape his American experience and his view of the American dream, and who do you think the different speakers in the poem are meant to be? What is he trying to communicate about himself, and other marginalized groups in the US, at the time the poem was written? What is he trying to reveal about the state of America to his readers?

Langston Hughes' famous poem, "Let America Be America Again," was published in Esquire magazine in 1936.
The poem takes the typical nationalist American poem, e.g., "America the Beautiful," and turns it into a criticism of American nationalism itself. In particular, the poem is written from the perspective of a non-white American citizen, whereas the typical nationalistic American poem is written from the perspective of a white person.
The poem itself is a criticism of the American identity, and Hughes illustrates that there are levels to that identity, or that the American identity itself is an illusion. For instance, the poem starts out praising the American people, landscape, and enlightened ideals—which Hughes genuinely believes in—but Hughes also points out, using irony and sarcasm as poetic techniques, that they only apply to certain segments of the country's population in 1935, when he first wrote the poem.
The different speakers in the poem are: the white privileged group of America and the other speakers, who offer a kind of rebuttal to the first group, are the minorities who don't have the same privileges. The poem starts out from the perspective of the former group and then Hughes articulates the perspective of the latter.
Hughes tries to communicate the different experiences of white and non-white peoples of the United States, especially in the context of the fictional American Dream. The colonists who won their freedom from the British Crown sang of being free, and yet Hughes asks, "The free? Who said the free? Not me?"
In the poem, Hughes also talks about the socioeconomic issues that many people in the United States faced during the Great Depression, which is around the time the poem was written. However, in this portion of the poem, Hughes does not indicate a particular segment or race, because he understood that even lower-class and middle-class whites suffered during the economic crisis.
A third poetic technique Hughes uses in the poem is repetition. For instance, he reiterates the masses of people who suffer from economic hardships and oppression by repeating the word "millions."

Who said the free? Not me? Surely not me?
The millions on relief today?
The millions shot down when we strike?
The millions who have nothing for our pay?

This particular verse offers the most vivid and affecting images throughout the whole poem. Hughes effectively emphasizes the differences in the American experience, and contrasts the first verses of the poem and the second-half.
https://poets.org/poem/let-america-be-america-again