In recent years, the US has imposed a series of initiatives such as high tariffs on China and even its Western allies, etc. Especially in 2018, the US introduced the Foreign Investment Risk Review Modernization Act, which further strengthened the security review of foreign investment, resulting in non-US companies with advantages being restricted from investing in the US. This paper argues that whether the US encourages or restricts local investment by companies from different countries is still a direct reflection of its foreign policy towards different countries, which has always oscillated between idealism and realism. Whether or not to pursue the ideological attitude of foreign investment, mainly depends on its security and economic goals, values of the goal of maximizing the interests of the integrated consideration, and its pursuit of strategic interests is above the pursuit of ideological goals. This paper will cite decades of U.S. treatment of investment enterprises in different countries, as well as whether the technological level of different enterprises let the U.S. feel the pressure of specific cases to analyze how the U.S. balance of ideology and national interests. Therefore, the consistency and conflict between foreign investment and U.S. national interests determine the realist position of the U.S. in the security review of foreign investment, i.e., to maximize U.S. national interests by seeking to obtain a balance between national interests and the transmission of ideology in the review.