WASHINGTON — The White House rolled out a sweeping national space policy for the United States on Monday, one that aims to boost international cooperation and reiterates plans to send Americans to visit an asteroid by 2025. The 14-page space policy reaches beyond President Barack Obama's plans for NASA — which would shift the goal of U.S. human spaceflight from the moon to visiting asteroids and Mars, according to a plan unveiled in February — touching on future needs for Earth observation, space debris and space security.