What literary devices is lee using when she has scout describe atticus’ trip to montgomery by saying, the governor was eager to scrape a few barnacles off the ship of state; there were sit- down strikes in birmingham; bread lines in the cities grew longer, people in the country grew poorer? " why are these statements significant?

Metaphor and allusion.  

These statements by Scout are significant for they show how the political upheaval during the racism and poverty of the Great Depression had affected the people of Maycomb and particularly the whole of Alabama.

Explanation:

Harper Lee's famous novel "To Kill A Mockingbird" revolves around the lives of the people in the South during the racial prejudice. The main protagonist Scout Finch and her family The Finches showed the true nature of things, also allowing us to see the society from the eyes of a little girl.

The excerpt given in the question is from Chapter XII of the text where Atticus had gone to Birmingham to attend the legislature of which he was a member. These lines spoken by Jean Louise 'Scout' Finch contains an allusion and even a metaphor in it. The use of these literary devices is to show how the lives of the people especially in her place of Maycomb, Alabama, were greatly affected by the Great Depression.

Alluding to the Birmingham strike, she gave details of just how the Birmingham strikes that protests against the racial discrimination, the poverty situation and almost all social issues, led to the upheaval in the state of Alabama. Thus, the use of allusions and metaphors by Scout shows the situation of the place during those times.