Rebuilding the United States-Flag International Fleet Act This bill revises and reinstates certain transportation requirements, including requirements related to the transportation of agricultural products. For example, the bill reinstates requirements that (1) at least 75% of gross tonnage of seaborne cargo for international food programs be carried on U.S. flagged vessels, and (2) the Department of Transportation reimburse international food programs for any cost premium under the U.S. flagged vessel cargo preference. Additionally, the bill revises provisions related to cargos procured, furnished, or financed by the federal government, including by authorizing the waiver of U.S. flag requirements for commercial vessels carrying such cargo when the vessels are unavailable at fair and reasonable rates.