President Joe Biden welcomed German Chancellor Angela Merkel to the White House on Thursday, in what is likely her last official visit to Washington. Biden is the fourth US president Merkel has dealt with in her 16 years in power, and he will be her last as she prepares to leave office later this year. Marco Werman takes stock of wrinkles that still beset the German-US relationship and what kind of Germany Merkel leaves behind with Constanze Stelzenmüller, a senior fellow at the Brookings Institution who specializes in German-US relations.