'America works as a place for Amir to bury his memories and place for Baba to mourn his.'... What is the function of irony in his novel?

In the book "The Kite Runner" Amir and his father escape from Afghanistan before the Taliban can get them.  Amir is happy to be in America because he longs for peace from what had happened to Hassan.  Yet, he can not escape the events that had happened that changed his life.  He is still an insomniac and he carries guilt over not standing up against Assef when he was raping Hassan.

Baba found America to be a place where he spent his time mourning his homeland.  The irony is that the homeland that he once knew ceased to exist.  He was mourning the life he once had, but the life was long gone.