Amir's mother that he's never known. She died giving birth to Amir and its played a big role in Amir's guilt.
Amir finally won the kite tournament and made Baba proud. All Amir's wanted was to make his dad proud and this is the way he "had" to do it.
Amir takes in Hassan's kid, Sohrab, and makes sure he gets the life he deserves. Amir had to go through a lot to get Sohrab.
When Baba and Amir finally arrived in the U.S., it was a very hard transition for Baba. He was seen as superior in Afghanistan, but in the U.S. he has to live just like everyone else. Their culture isn't what it is in Afghanistan.
After Amir promised Sohrab he'd never return to an orphanage, he found out he might have to break that promise to get him to the U.S. Sohrab was so down on the news, he attempted committing suicide.
This is not the Golden State Bridge, but that is definitely one thing that Sohrab was excited to witness for his trip to the U.S. Amir told him about this foreign land and he became hooked with the bridge.