By COLLEEN LONG
WASHINGTON (AP) — Jill Biden has used her first solo White House event as first lady to highlight the challenges and contributions of “hidden heroes” — the children and caregivers of injured U.S. troops. Biden says that “from a young age, hidden helpers learn the cost of our wars up close.” The first lady said she often visited Walter Reed military hospital in 2009, when wars were raging in Afghanistan and Iraq. And she recalled building relationships with the families of those injured in wartime. Biden says that U.S. troops and their families “need to know that if they ever face injuries, illnesses or wounds,” Americans will have their backs.