There is more on the inside - Like the lead casket which contained the permission to marry Portia and to obtain her fortune. This connects to the underground of New York City which contains a complex network of tunnels, sewers, and subways.
The geography - Both New York City and Venice are important port cities to their countries. New York City also has certain segregated areas such as Chinatown and Little Italy, this can be connected with the different places Jews and Christians lived in Venice had.