The connotative meaning of the "fault lines" in the excerpt is something that is powerful and threatening to others.
Explanation:
Anna Quindlen, a Pulitzer-Prize winning author wrote a commentary on the Sept 11 bombing for the <em>Newsweek</em>. In her article "A Quilt Of A Country", she points out that America is home for many nationals who had come there to get a new start or a better way of life. And with this diversity, there is also unity. So, when there are threats of any kind, these different nationalities all come together, united against the common enemy. There may be "fault lines" that demarcates and separates people to people, but in times of crisis and common fight against evil such as terrorism, people forget their national identities and become Americans first. And this is what makes America great in comparison to any other country.
