DAKAR, Senegal (AP) — The United States is sending troops to Nigeria to help train the West African nation's military in fighting extremism, Nigerian authorities said Wednesday, as a multifaceted security crisis spreads in the north of the country.The American personnel won't engage in combat or have a direct operational role, and Nigerian forces will have complete command authority, Maj. Gen. Samaila Uba, spokesman for Nigeria’s Defense Headquarters, said in a statement.“At the invitation of the Government of Nigeria and in continuation of our longstanding security cooperation and military-to-military partnership with the United States, Nigeria will host a contingent of...