the Stranger: he  has typical features of americans as regards the physical appearance and the bearing

Princeton:  it represents  america' s college life ,with " beautiful campus, professor who are titans in their fields and fellow students who are philosopher -kings in the making"(page 3). it represents" the power of that pragmatic and effective system in America". (page 4)

Underwood  Samson & Company: a valuation firm Changez works for, which gives him useful skills. It represents America and the capitalism system.

Changez's friends and Erica : They represent the power of America because even if they are abroad , they feel happy and wealthy. This is because America is one of the most powerful and wealthiest country in the world. Also as concerns Erica, one understands that she is the personification of America. Indeed, the name "Erica" is included in the word "America". She represents the American's dream.