This paper quantifies the rerouting of China’s wood and paper sector value added to the United States over 2016–2022, a period spanning the imposition of U.S. Section 301 tariffs and subsequent supply-chain reorganization. Using OECD ICIO, a three-term value-added decomposition separates direct bilateral from indirect trilateral flows through third-country transit economies. A structural decomposition analysis attributes changes in the trilateral channel to four factors: value-added intensity, China’s domestic supply-chain structure, China’s intermediate export orientation toward transit economies, and transit-economy global value chain output combined with U.S. final demand. The trilateral channel grew by 125.5% in wood and 159.4% in paper over the study period, substantially exceeding bilateral channel growth. China’s active reorientation of intermediate exports toward transit economies emerged as the dominant supply-side driver. Vietnam, Mexico, and Canada are identified as the principal conduit economies. Value-added RCA consistently exceeded gross-trade RCA in both sectors; in paper, the gap widened throughout the tariff period, indicating that China’s upstream international competitiveness strengthened despite bilateral trade barriers. These findings demonstrate that bilateral tariffs are materially less effective than gross-trade statistics imply. Value-added tracking should accompany gross-trade monitoring in trade policy assessment.