The US supported Chaing Kai Shek and the Nationalists over Mao and the Communists after WWII. Also, Mao was a staunch Stalinist so there is the holdover tension there. Mao continued with that even more so after Stalin died and was determined to be basically the Stalin of Asia.

Also China was abused by the west prior to that, though mostly Europe so there is probably no love lost there.

I would recommend Frank Dikötter books on China, The Tragedy of Liberation, Mao's Great Famine, and The Cultural Revolution.