This is a great question. The most important political event in the book is the fall of the monarchy in Afghanistan. As soon as the king is ousted, there is gradual chaos. The Soviet Union eventually moves in and the Taliban gain local power over Kabul.
In light of this the changes are great. Amir and Baba become refugees as they seek to escape. They finally make it to the United States, California. And they are now forced to live a new life. The life they knew is Afghanistan is now gone. This change is especially hard for Baba.
As for Hassan, he is eventually killed by the Taliban. Amir learns about Hassan's fate later on in life. Hassan was not able to escape. So, his fate was death.
As for Assef, he joined the Taliban. From the perspective of Amir, he was part of the political problem. He is part of the oppression of a once beautiful country.
So, we can say that the political events completely changed the lives of all the major characters.