What external conflicts exist with Amir and Hassan in The Kite Runner.
One of the first external conflicts is introduced in Chapter 5 as Amir and Hassan run into Asef and some of his bullies and Assef taunts them both, calling them homosexuals, etc. This external conflict is escalated in Chapter 7 as Hassan is caught while running the kite and Asef rapes him because he will not give up the kite.
Another example of an external conflict is the Soviet invasion of Afghanistan but this isn't really central to the plot as much as the previous conflict.
You also have the external conflict between Amir and Asef that does not end until Chapter 22 when Asef beats Amir to a pulp and only stops when Sohrab shoots him in the eye with his slingshot.