I believe the linking verb is “will”. It’s linking the subject “the United States of America” and the predicate “be 300 years old!”
Answer:One of Us Is Next takes readers back to Bayview High a year after Simon's death, and no one's been able to satisfy the gossip hunger quite like he could. ... In One of Us Is Next, fans will learn what the Bayview Four are up to and meet intriguing new characters who will keep them turning the pages.
Explanation: