American Families United Act This bill limits what constitutes a conviction for immigration purposes and contains other related provisions. (A conviction can in certain instances be grounds for denying an individual immigration benefits.) Under this bill, certain judgments of guilt, such as one that has been deferred, expunged, or invalidated, shall not be considered a conviction for immigration purposes. An order of probation without an entry of judgment shall also not count as a conviction. Similarly, a pardon shall render the underlying conviction null for immigration purposes. Furthermore, for immigration purposes, a term of imprisonment shall only include the actual period of incarceration ordered by a court. If a term of imprisonment is suspended for any length, the suspended time shall not be considered as part of the term of imprisonment. (An individual may be denied certain immigration benefits if the individual has been convicted for a crime with a certain term of imprisonment.) The bill also provides statutory authority for the Department of Justice and Department of Homeland Security to, in certain instances, exercise discretion when enforcing immigration laws, such as waiving one or more grounds of inadmissibility or declining to order an alien removed. Such discretion may only be exercised on a case-by-case basis for humanitarian purposes or to preserve family unity and is subject to other limitations.