The principal aim of U.S. President Barack Obama's recent Asian tour obviously was to reconfirm his "rebalance policy" and "pivot to Asia." At a joint press conference in Tokyo with Prime Minister Shinzo Abe on April 24, Obama stated that the Japan-U.S. Security Treaty would apply to the Senkaku Islands in the East China Sea, which are also claimed by China. This was good news not only for Japan but for the Philippines and other nations in the region having territorial disputes with China in the South China Sea.
At the same time, Washington tries to construct multifaceted bilateral ties with Beijing, often referred to as a "new-type relationship between big powers."
This brings up a question of how such Sino-American ties would affect longtime alliances between the U.S. and some Asia-Pacific countries. If relations between the U.S. and China improve, the significance of those alliances would become smaller. Should China cease to be a military threat to the U.S., those alliances would lose their raison d'etre.