For Prime Minister Shinzo Abe, Thursday's summit with U.S. President Barack Obama should have been a big moment to trumpet the strength of the Japan-U.S. alliance, which he claimed has greatly improved after relations soured under the Democratic Party of Japan-led administration that preceded his.

But the diplomatic drama that unfolded from Thursday night to early Friday instead underscored that bilateral relations are shaky, despite Abe's insistence that he and Obama made "historic" achievements. The key problem is the failure of both nations to reach a broad accord on the Trans-Pacific Partnership trade pact.

On Friday, Japan and the United States barely managed to release a joint statement following Thursday's Abe-Obama summit in Tokyo, an unprecedented and embarrassing delay for Japanese diplomats.