THE U.S. Coast Guard imposed a temporary security zone in waters off South Carolina during the military's search for debris from a suspected Chinese spy balloon shot down by a U.S. fighter jet, and the White House said it would keep a calm approach to relations with Beijing. President Joe Biden told reporters it was always his view that the balloon needed to be shot down and brushed off a question about whether the incident would weaken U.S-China relations. "No. We made it clear to China what we're going to do," he said. "They understand our position. We're not going to back…