Structure in an American in Paris

The piece 'An American in Paris' is broadly divided into two aspects: the Paris of the daytime, where the protagonist is happily marching down the Champs-Elysees, or around the city's cafes. Then there is the night-time Paris, full of smokey jazz clubs (we hear a melody reminiscent of the Blues being played throughout). 
There is a lot of repetition throughout the work, in particular the main melodies, like the walking theme (that we hear first in the very beginning), the taxi-cab theme (played by the horns in figure 3), the can-can theme (figure 11), walking theme 2 (figure 13), and the night-time Blues theme (figure 48). These melodies are often repeated in other instruments, so that their timbres are changed, thus the impacts of the melodies are enhanced. This reinforces the overall idea of the two main aspects in the piece. 
The aforementioned melodies fit into the two categories I talked about earlier, with the majority fitting into the daytime aspect of Paris. It is as though the protagonist sees the daytime Paris regularly during his stay, and only rarely gets to experience the night-time goings on, which are far more exotic and enthralling. 
The melody for the night-time is reminiscent of typical American Blues, showing that perhaps the protagonist is projecting his Americanised views onto the Parisian night.
Gershwin does not finish his masterpiece, however, without bringing back every theme for a final, somewhat nostalgic farewell, as though the protagonist is finally saying goodbye to every part of Paris that he has been to before he leaves. This last part of the piece is, however, far more excited, and we finally get some soaring melodies, as though to suggest that the airplane is departing. Gershwin leaves us with the night-time melody ringing in our ears before his final, incredibly grand, cadence, as if to say "Remember the excitement held in the depths of Paris!"