In The Distance Between Us, why was it so important when Reyna Grande's father took the three siblings to the United States?

The decision that Reyna’s father made was especially important for her because it meant that she grew up in the United States rather than in Mexico. Although she was not US-born, she lived there from age eight and so developed an identity that was more closely linked to her experiences among other children who were raised there. Her memories of Mexico began to dim, so much so that upon returning, she felt more of an outsider there.
A second area of significance, however, is that for her father, the transition was much more difficult. Racism and higher educational and training requirements blocked him from many jobs; his descent into depression, drinking, and abusive behavior had a negative effect on Reyna and her siblings. These childhood experiences gave her ambivalent attitudes toward both her father and US society.
https://www.simonandschuster.com/books/The-Distance-Between-Us/Reyna-Grande/9781451661781