BERLIN—More than 60 people have died and dozens were missing Thursday as severe flooding in Germany and Belgium turned streams and streets into raging torrents that swept away cars and caused houses to collapse. Among those killed were nine residents of an assisted living facility for people with disabilities and two firefighters involved in rescue efforts across the region. “I grieve for those who have lost their lives in this disaster,” German Chancellor Angela Merkel said during a visit to Washington, expressing shock at the scope of the flooding. Speaking alongside U.S. President Joe Biden at the White House, Merkel said her thoughts were with all those who had lost loved ones or were still searching for them. “I fear the full extent of this tragedy will only be seen in the coming days,” she said. Biden likewise paid his condolences for the devastating loss of life and the destruction …