After 31 years with the U.S. State Department, and witnessing the transition of six presidents and six secretaries of state, Roberta Jacobson can say with certainty she has never seen anything like the transition into the Trump administration.Jacobson, who served as the U.S. ambassador to Mexico from April 2016 to May 2018, says President Donald Trump’s comments when he was a candidate, such as calling Mexican nationals who come to the U.S. rapists , made relations between the two countries difficult, and more challenging for diplomats like her.“This is an . . .