U.S is a large land and powerful so they are involved in many historic events. Plus they have different resources and goods.
Answer:
Family/environment and personal values
The lines which are a flashback here are: She thought of her last day in middle school, seven years ago, when Sarah had given her an iPod. She had felt ecstatic that day when she realized she would be able to listen to her favorite songs and fend off comments from her cousins about how little she knew about music.
