The few times they are treated badly it is not because they are immigrants but because of their race. E.g. when Selina is distubred by the racial slur of her dancing partner's mother.Also they are subjected to the cast-off clothes of their employers.
However, the novel is not really about that because it focuses on a young girl who is born in America. She desires to go to a C/bean that she does not know with her father but her mother shows her the hardship associated with the C/bean of that time.
therefore the novel focuses more on the exerience of Selina growing up 1. among immigrants 2. in an unhapbpy home 3. and the difference experiences that shape who she becomes as an adult.
Remember the book is a bildungsroman, a novel of initiation.