When Amir and Baba move to the US their relationship changes, What are the changes in their relationship?In Hosseni's novel 'The Kite Runner.'

Under the stress and precarity of immigration, Amir sees his father in a new light. He realizes his father's weaknesses and vulnerability, and the very absence of the aura of omnipotence brings father and son together in a new way.

Baba, too, changes for the better. He is more approachable, he spends more time with Amir, and when Amir takes an interest in Soraya, Baba goes the second mile to see that the courtship and ensuing marriage are done "properly," the Afghan way. Even when he is so weakened because of his cancer, he sees to it that all goes well for the new couple, even though he could have rejected Soraya because of her tainted past.

Adversity of cirumstance unites the two in a way that would probably have not happened otherwise.  Baba never breaks down to confide to Amir about Hassan also being his son, but he does everything else possible to make ammends for the errors of his youth, including his shortcomings as a father.