American Families United Act This bill authorizes the Department of Homeland Security (DHS) or the Department of Justice (DOJ) to exercise discretion in certain immigration cases. The bill also removes certain requirements related to birthright citizenship. Under this bill, DOJ or DHS may, on a case-by-case basis, exercise discretion by declining to remove an alien or bar an alien from entering the United States to prevent hardship for the alien's U.S. citizen spouse, parent, or child. However, DOJ or DHS may not exercise this discretion if the alien is removable or inadmissible due to certain grounds, including specified crime- and security-related grounds. The bill also removes certain requirements related to birthright citizenship for a child born outside of the United States to one U.S. citizen parent and one alien parent. Specifically, the bill removes a provision that requires the U.S. citizen parent to be physically present in the United States for at least five years before the child's birth in order for the child to acquire U.S. citizenship at birth.