The first 1 minute and 23 seconds of this are beautifully adapted from the main theme of Morricone's "Once upon a time in America" ("Deborah's theme"). Well, the first line of the vocal melody of this is actually directly lifted from Morricone's first line, but we won't over-emphasise the point. (I just hope Ennio got his royalties!). The vocal performance of Shane McGowan of the Pogues is something one can either see some merit in or not, but it has a certain musical expressiveness.
The same "Deborah's theme" is used again repeatedly in the second half of the track, particularly the instrumental fade, but nowhere with the effectiveness of the first 1:23.