American Memorial Park Annex in Tinian Act - Directs the Secretary of the Interior to develop an annex in Tinian, Commonwealth of the Northern Mariana Islands, as an extension of the American Memorial Park on the island of Saipan. Requires the annex to be used to interpret the important aspects of the North Field Tinian by highlighting the historic events related to the Mariana Islands Campaign during World War II and to serve as a curatorial storage of artifacts of World War II.