Answer:
They believed immigrants were undermining American society.
Explanation:
The Know Nothing Party (officially known as the Native American Party, and then the American Party) was a political party that existed in the United States in the mid-1850s. This party was anti-Catholic and anti-immigration, and generally displayed a dislike for immigrants. Because of the secrecy of the party, members generally answered with the phrase "I know nothing," leading to the party's nickname.
