MANILA, Philippines — China has failed to intimidate rival claimant states into surrendering their sovereign interests in the disputed South China Sea despite its intensifying “bullying tactics” and the United States and other allied countries are ready to further boost deterrence against Beijing’s aggression, the U.S. Pacific Fleet commander said. Adm. Stephen Koehler, who oversees the largest naval fleet command in the world, gave assurances Friday in a Manila forum of U.S. commitment to help