The American Citizenship Act would change how the United States grants citizenship to people born in the country. Currently, anyone born in the U.S. automatically becomes a citizen regardless of their parents' immigration status. This bill would modify that rule so that children born in the U.S. would only receive automatic citizenship if at least one parent is a U.S. citizen or a lawful permanent resident at the time of birth. The legislation would apply only to people born after the law takes effect, leaving the citizenship status of people born before the enactment date unchanged. The bill aims to redefine what the Fourteenth Amendment's citizenship clause means in practice by amending the Immigration and Nationality Act.