This is a complex question and one that I will need to break down into various elements.
Setting - The central setting and the recurring structural motif of the novel relate to the interactions of various characters both with the day of the tightrope walking incident and with viewing this incident in person. It is, for example, the day on which Corrigan dies, the character at the centre of the first section of the novel. However, the nature of the story is that it traverses different parts of New York in terms of physical setting, from the projects of the Bronx in the first section, through to the Upper East Side in the next section, through to Rikers Island and upstate New York, the home of the artist couple who crash into Corrigan and Jazzlyn and, indeed, the computer programmer who contacts downtown New York to gain eyewitness accounts of the tightrope walker. The setting is, of course, a collection of inter-related short stories, meant to provide a cross-section of New York at one of its defining periods, using the motif of the tightrope walker as an image to discuss both the connections between different people and places and the precariousness of human life.
There is also the temporal setting of the novel which is, at one level 1974, the day of the tightrope walking incident. However, the setting also has echoes of the present. One might, for example, take the thinness and illness of Corrigan and the blotches on his body - these are, of course, at a time before the AIDS epidemic but, in the setting of promiscuity and intravenous drug use, the modern reader sees the early signs of these things to come just as the interlinked sections with computer programmers and hacking into telephone exchanges pre-figures new forms of connection via the internet. McCann consciously uses this setting temporally to forge connections between the present and the past too.
Culture There are, of course, a wide array of different cultural elements to the novel and these are consciously designed to show the multi-cultural elements of New York, both in the 1970s and for today's readership. The first of these is close to McCann's own upbringing as an Irishman now working in the USA - Corrigan's and his brother Ciaran's journey to America are for different reasons. Corrigan moves in order to seek the poor (an ironic reversal of the usual reason, to seek wealth) while Ciaran moves in order to avoid trouble at home. Both represent different facets of Irish migration to the US. However, we get numerous moments of cultural juxtaposition within the novel and often extreme cultural distinctions are placed next to one another such as, for example where we move from the Corrigan's account, amongst the prostitutes of the Bronx to Claire and her upper class home on the edge of Central Park. Other cultural juxtapositions and connections come between Jazzlyn and her mother, representatives of poor African Americans, and the bohemian artist and daughter of a rich industrialist who is in the car that kills Jazzlyn. All are connected by an accident just as all of the characters are connected both by the city in which they live and by the events taking place around the day of the tightrope walking incident, the central symbol of connection in the novel.