President Barack Obama urged Americans to remain united in the face of terrorist attacks 15 years after 9/11. Obama said in his weekly radio and online address, delivered on the eve of the 15th anniversary of the September 11 terror attacks, that in the face of terrorism, how America respond matters. He said the US cannot give in to those who would divide it. Mr. Obama added, its diversity and welcoming of all talent is what makes US resilient.<br/>More than 2,750 people were killed when two passenger jets destroyed the Twin Towers, the symbol of New York's financial wealth and confidence. Another jet slammed into the Pentagon, and a fourth jet crashed in a field in Pennsylvania after those on board tried to overpower the hijackers.<br/><br/>