There is an ongoing debate about supply chain linkages between African and foreign firms and the impact of GSCs' activities on African states. This chapter contributes to the discussion by studying the impact of the US and Chinese presence in the Southern African Customs Union (SACU) region, via supply chains, on economic growth and development comparatively. It argues that the expanding supply chain trade, especially the rapidly growing trade with China, is diversifying intermediate goods and services exports from SACU states and expanding their industrial capabilities. Politically, SACU is at an inflection point; initial gains from GSC trade could spur further economic liberalization or could incentivize ruling coalitions to double down on inward-looking policies. The chapter also highlights some emerging trends in SACU supply chain trade with the two great powers, using intermediate goods and services trade data. It ends with a discussion of the impact of the Covid-19 pandemic on supply chains in the SACU region.