Iran killing, U.S. troop cuts could make Mideast thornier for Biden

Read MoreThe new president will take over with a shrinking U.S. military footprint eroding trust, and Tehran vowing to take revenge for a brazen assassination it blames on Israel.The new president will take over with a shrinking U.S. military footprint eroding trust, and Tehran vowing to take revenge for a brazen assassination it blames on Israel.