Final answer:
Case studies such as the Alger Hiss case and the Rosenberg case provided concrete evidence of espionage activities and raised concerns about Soviet infiltration of the American system.
Step-by-step explanation:
The main reason that case studies were considered important in convincing people that Soviet spies were infiltrating the American system is because they provided concrete evidence of espionage activities.
Case studies, such as the Alger Hiss case and the Rosenberg case, involved individuals who were accused of spying for the Soviet Union and were found guilty. These cases generated widespread public attention and raised concerns about the extent of Soviet infiltration.
For example, in the Alger Hiss case, a former communist spy named Whittaker Chambers accused Alger Hiss, a State Department official, of spying for the Soviet Union. Chambers led officials and reporters to microfilmed documents that were allegedly typed by Hiss and passed on to his Soviet contact.
Although it was impossible to prove conclusively that the documents were created by Hiss, the nature of the accusations led to a trial and Hiss was convicted of perjury.
The Rosenberg case was even more impactful because it involved the fear that the Soviets had stolen the secret of the atomic bomb. After learning that the Soviet Union had exploded an atomic bomb in 1949, many people wondered if the Soviets had acquired the knowledge through espionage.
Julius and Ethel Rosenberg were accused of being part of a spy ring that passed classified information about the atomic bomb to the Soviet Union. Even though their guilt is still a topic of debate, their case heightened fears of Soviet infiltration.