Final answer:
The passage of the Espionage Act and Sedition Act during World War I significantly restricted American First Amendment rights by limiting freedom of speech and leading to the prosecution of over two thousand individuals.
Step-by-step explanation:
During World War I, American First Amendment rights were affected by the passage of the Espionage Act and Sedition Act, which restricted freedom of speech. The Supreme Court upheld these acts, establishing the 'clear and present danger' test which limits free speech that poses a direct threat to the security of the United States or its military operations. These acts allowed for heavy fines and imprisonment for those who used 'disloyal, profane, scurrilous, or abusive language' against the government or the war effort, and over two thousand individuals were prosecuted under these laws.