There are significant differences between China and the United States in both the evolution and characteristics of their cross-border data flow policies. Security first and market-led reflect two traditional models of cross-border data flow rules in China and the United States, yet in an era of AI-driven great-power rivalry, these regulatory systems increasingly diverge from their original patterns. The transformation of the global governance landscape for cross-border data flows is underpinned by three fundamental dimensions of major-power competition: technological capabilities, development models, and discursive power. In particular, a comparative analysis of the evolution of China-U.S. cross-border data flow rules shows that these phenomena and their underlying logics simultaneously embody a shift in the two countries’ strategic positions within global value chains, especially in their contest for dominance over AI technologies. These changes exert a profound impact on domestic technological and economic development, while laying a new foundation for the future trajectory of global data governance. Whoever succeeds in designing cross-border data flow rules that are conducive to AI development will gain the upper hand in global AI competition. China’s trend toward greater openness is driven by the demands of corporate globalization and technological autonomy, especially the growing need for data to support AI innovation; the United States’ increasingly conservative stance is shaped by technological ethics and international competition, particularly its strategic adjustments in the field of generative AI. Together, these dynamics are pushing the global data governance order toward a more multipolar configuration.