Overview: Wednesday on the NewsHour, tensions rise in Asia as the U.S. partners with Australia and the United Kingdom to curb Beijing's ambitions. Then, U.S. gymnasts testify before Congress about the FBI's botched investigation of sexually abusive doctor, Larry Nassar. And, the U.S. struggles to contain the flow of the high-powered opioid fentanyl across the southern border amid a raging addiction crisis.