In April 2025, the United States launched a new round of global tax restructuring plan to promote the implementation of a "reciprocal taxation" mechanism for multinational trading partners, which quickly triggered the introduction of countermeasures by China. The institutional reshaping of global tax rules constitutes a new source of external shocks, which strengthens the arbitrage motive and profit-seeking behavior of international capital in the short term, and triggers the cyclical mismatch and structural transition of cross-border capital flows. Compared with the traditional theoretical analysis path based on interest rate spread and exchange rate fluctuations, such institutional shocks are more likely to cause changes in policy expectations, emotional amplification effects and non-linear responses of market adaptation mechanisms, and traditional methods are difficult to effectively identify their dynamic evolution process. This paper focuses on the asymmetric adjustment mechanism of China''s short-term cross-border capital flows in the context of the global tax game. Based on the quarterly data from 2008 to 2024, this paper constructs a multi-threshold regression model, introduces generative artificial intelligence to conduct semantic modeling of policy texts, and constructs the policy Semantic Strength index (TPSI). Systematically identify the structural transition path of capital flows and the time-varying effects of regulatory policies. The results show that: (1) the global tax shock significantly changes the structure of capital''s response to interest rate spread and exchange rate expectation, showing the characteristics of interval transition and asymmetric response; (2) TPSI generated by generative AI has a significant lead in identifying the direction and flow trend of capital sentiment, making up for the lagging response of traditional variables to changes in policy expectations; (3) In the high semantic intensity range, the regulatory effect of the current macro-prudential tools is weakened, and there is a risk of "high-frequency unanchoring" and lagging regulation of short-term capital flows. Based on this, this paper proposes to establish a cross-border capital early warning mechanism based on semantic expectation recognition, improve the governance capacity of capital flows prospectively, and actively participate in the restructuring process of global tax rules, so as to enhance the institutional resilience of countries in the international financial system and the ability to safeguard tax sovereignty.