How does hughes’ poem, “let america be america again,” represent the idea of the failure of the american dream?

The beautiful poem "Let America be America Again", by Langston Hughes, contrasts the America that was dreamed of by those who crossed the oceans to colonize it to what America really is.

The American dream is one of freedom, of equality, of opportunities. America was supposed to be free of tyrants, of exploitation; it was supposed to be the land where all men have equal chances to succeed in life. However, as the speaker says, 'America was never America to me'.

The real America is the exact opposite, a land colonized and enriched by the work of those who were torn from their land and brought in by force. It's become a land where a greedy few get wealthier, while those who work to make them so die in poverty and sickness. As we can see in this excerpt:

Say, who are you that mumbles in the dark?  

And who are you that draws your veil across the stars?

I am the poor white, fooled and pushed apart,

I am the Negro bearing slavery’s scars.

I am the red man driven from the land,

I am the immigrant clutching the hope I seek—

And finding only the same old stupid plan

Of dog eat dog, of mighty crush the weak.

i've read it so how can i ?