Why did America fears about the spread of communist intensify after the communist victory in the Chinese civil war?

America's fears about the spread of communism intensified after the Chinese civil war victory in 1949 because it represented a significant expansion of communist influence in Asia, undermining U.S. interests in the region. The success of the communist forces in China was perceived as a validation of Marxist ideology and a potential catalyst for similar movements in other countries, particularly in Southeast Asia. This led to heightened concerns about a "domino effect" where one country's fall to communism could trigger others to follow, reinforcing the U.S. commitment to containing communism globally. Additionally, the alignment of China with the Soviet Union further alarmed American policymakers, as it suggested a stronger communist bloc that could challenge U.S. hegemony.