The Senkaku Islands geographically appertaining to Taiwan were ceded concomitantly with Taiwan to the Emperor of Japan as per the Treaty of Shimonoseki. China refuses to recognize Japan's territorial claim on January 14, 1895 but admits Japan acquired formal title on May 8, 1895.
The terms of the Cairo Declaration nullified due to Chinese intervention in Korean War were unable to be carried out.
The Peace Treaty concluded between Allied Powers and Japanese Government is not concerned with Japanese Emperor's title over any integral part of Japan including the connected islands of Senkaku and Taiwan.
It is improper for US Government to veil the legal status of the Senkaku Islands by taking no position on ultimate sovereignty, leaving room for a territorial dispute between China and Japan.