According to a Japanese news show, China is angry with the USA for "provoking" North Korea.
I was talking with my wife about this the other night, and this was the analogy I made for her: The world is a neighborhood block. In the middle of the street Li'l Kim is shouting obscenities and threatening violence against the neighbors. A group of teenagers and men go down and surround the kid. They're not doing anything, but they don't know whether or not to take him seriously. Meanwhile the old lady down the block, Mrs. China, is yelling from her upstairs window, "DON'T YOU DO ANYTHING TO THAT KID. LEAVE HIM ALONE. YOU ARE BOTHERING THAT KID."
Seriously, wtf.