The except speaks of the potential of national unity in the United States being shattered as a result of a lack of a common enemy that the World Wars and Communism gave them.
The Fault lines in the excerpt refer to demarcations between opposing sides in the World Wars and in the Cold War that people then gathered behind to fight against their enemy. This made these lines become Areas of defense in essence that everyone came behind in solidarity to defeat their World War and Cold War enemies.
Hyperbole it's exaggerating it's not metaphor or simile since it's not comparing two things and personification is giving human like qualities to inhuman things and it's not doing that either
