While the US–China trade war caused Chinese exports to the United States to drop, the contraction was far from uniform across products. Analyzing HS8-level export data within a causal forest framework, we demonstrate that China's pre-war revealed comparative advantage (RCA) in the US market is the dominant driver of treatment-effect heterogeneity. Variable importance and best linear projection analyses confirm RCA’s central role. Partial dependence plots reveal a non-linear threshold: export drops are moderate at low RCA levels but steepen significantly once RCA hits 3.5 or higher. Complementary difference-in-differences panel regressions confirm this pattern, showing that high-RCA products suffered disproportionate contractions. Together, our findings reveal that tariff shocks impose the greatest displacement pressure on goods where the exporting country initially enjoyed the strongest market position.