Answer: to show that despite its differences, America is still a country that unites in times of strife.
The reason why Anna Quindlen wrote "A Quilt of a Country" was to show how America remains united even in difficult times. This article was written during the aftermath of the September 11 attacks, and this was a time when diversity began to be seen as a fracture, or a problem, of an otherwise healthy society. Quindlen wants to disprove this, and she argues that diversity is in fact a strength, and that America is strong despite the differences of its citizens.