In The Kite Runner, how does the relationship between Amir and Baba change when they move to America?

When Amir and Baba left Afghanistan, Amir was still a
young boy. During the time he and his father spent in California, Amir grew into a
mature, confident young man. He continued his love of writing and eventually graduated
from college and got married. This transition from boy to man sat well with Baba, and he
came to admire his son. The two of them lived together and bonded as they had never done
in Kabul, sharing their weekends and working at the San Jose flea market. Although Amir
never grew into the strong, physical man that Baba had been (and had hoped for in his
son), the son made his father proud, and the two men grew closer than they had ever
been. Amir's engagement and eventual marriage to Soraya gave Baba one last gift of
happiness, presenting him with a daughter (-in-law) that Baba never had, as well as a
closer relationship with General Taheri, who like Baba, had been a powerful man in his
homeland before immigrating to America. Just as Baba had taken care of Amir when he was
young, Amir tended to Baba in his final days, and Amir's love for his father was evident
at the end--something that was not always present as a boy growing up in
Kabul.