USA is finding trouble with China again after its failed attempt at South China Sea issue.

http://www.scmp.com/business/global-economy/article/1990051/us-china-clash-over-market-economy-status-wto

ASEAN and EU know about the illegitimate status of PCA and the judgement and are silent about the South China Sea ruling.  Therefore, USA knows it has failed in its attempt and decides to attack China in WTO.