"The Pilgrims signing the compact" is in fact an illustration that depicts the moment when the Mayflower Compact was signed. Although this illustration has value, it provides little information about this event. It is not possible, for example, to know through illustration who signed the pact and for what reasons it was established.
Therefore, we cannot agree that the illustration "The Pilgrims signing the compact," helps historians to understand what happened during the signing of the Mayflower pact.
I think it is the first one (shoppers find sushi...). Cultural diffusion refers to the spread of different cultures around the world. Finding Asian food in America definitely shows an example of cultural spread.