Complex sentence: Seeger visited Communist China and as a result had her US passport withdrawn; the US State Departmentwhich had been opposed to Seeger's trip to Moscow, where the CIA had monitored the US delegationwas incensed that Seeger had gone to China against official "advice".
Split into simpler sentences: Seeger visited Communist China and as a result had her US passport withdrawn. The US State Department, which had been opposed to Seeger's trip to Moscow (where the CIA had monitored the US delegation), was incensed that Seeger had gone to China against official "advice".