What was the impact of the setting on the plot of the novel "Bud, Not Buddy"?

The setting carries the plot, enhances it, and shapes it. The Depression was a time of despair all over the United States, and because of it, Bud ended up motherless, fatherless and homeless. Living in Michigan in 1936 was hard on mothers who tried to take care of their children while the fathers went away, chasing illusive dreams of work.

Bud had to escape foster care due to mistreatment born of discrimination. The setting of the Depression in a city carries the plot as Bud finds he cannot escape the state and decides to find his father. It enhances Bud's homelessness as no one has any way to help him, as they can hardly help themselves. 

The setting shapes the plot, providing a framework for the story. The experiences Bud had would make far less sense. The plot would lose the ability to evoke a sense of gloom and disappointment if set in a different time or place.