Immigration Could Be Curtailed By Simply Enforcing This Law.
U.S. Code 8 USC 1423
Requirements as to understanding the English language, history, principles and form of government of the United States.
No person except as otherwise provided in this subchapter shall hereafter be naturalized as a citizen of the United States upon his own application who cannot demonstrate an understanding of the English language, including an ability to read, write, and speak words in ordinary usage in the English language.
https://www.govregs.com/uscode/title8_chapter12_subchapterIII_partII_section1423