LOS ANGELES (TheWrap.com) - John Mayer is piping up for America's veterans. The "Waiting for the World to Change" crooner made a stop in Washington D.C. on Wednesday to attend the Grammys on the Hill event, where he was one of the night's main attractions. Mayer was honored for his efforts to support veterans in their transition back to civilian life, along with his work in promoting music education programs. On the red carpet at the Liaison Capitol Hill hotel, Mayer took a moment to talk about promoting his two causes on Capitol Hill. ...