Hey there,
Based on the passage listed: And whether it is a farmer arriving from Italy to set up a small grocery store in a slum, or a young girl arriving from a small town in Mississippi to escape the indignity of being observed by her neighbors, or a boy arriving from the Corn Belt with a manuscript in his suitcase and a pain in his heart, it makes no different.
Your question states: What effect does imagery have on the meaning of "Here Is New York" by E.B. White? Your correct answer would be The vivid imagery describes the vitality of the city and the passion that unifies those who make New York their home. By the people who make NY their home, they basically make the vivid imagery vitality of the city, with a passion.
Hope this helps.