>"China has indisputable sovereignty over the islands in the South China Sea and their adjacent waters," Tian reportedly said.

The Spratly Islands are recognized sovereign territory of various sovereign nations, including Taiwan, but not including China. Their geographical location is also closer to Taiwan than that of Mainland China. They do not own the ocean, nor do they have any right to claim the US violated their international waters in an area that is no way a part of their territory.

China does have military installations on several islands, but Japan isn't US territory because it has a US military base, just like none of those islands are officially recognized as China's.