Answer:
Anna Quindlen considers that America is "an improbable idea", because it was created with the idea of equality between men, but it is impossible to maintain this equality within so much diversity.
Step-by-step explanation:
To support this idea Quindlen shows that America is a mixed-race nation, very diverse and without a cultural and racial unity in its territory. This stimulates the social difference between people, completely removing the issue of equality, when a group of individuals considers themselves superior to other groups because of their cultural differences and differences in values and customs.