Answer:
One cause of the hysteria was the surprise attack on Pearl Harbor by the Japanese on December 7, 1941. This resulted in immediate shock and fear among the American public, which led to a sense of panic and suspicion. The long term effects of this decision were an increase in public support for the war effort, and an increase in militarization and security measures. This caused the public to become more suspicious of any foreign activity, and increased the level of paranoia and distrust towards foreigners. This in turn led to the internment of Japanese-Americans, as well as increased surveillance and monitoring of foreign activities. Additionally, this hysteria led to the enactment of the Espionage Act of 1917, which allowed for increased monitoring of various activities, and was used to target dissenters and anti-war activists.