A Nation's Sin?

Genesis 20:8-18 So, exactly what did Abimelech do wrong? What was his sin? Abimelech considers the sin into which he's fallen to also be the sin of his kingdom. What is this thing about national sin? What ought to be our response to the sins of our nation and our leaders? Abraham's troubles here began with his prejudice. What is the nature of prejudice, and what forms does it take in our lives? How is Abraham like the Church?