The head of U.S. Citizenship and Immigration Services is stepping down from his post next month per the request of President Trump, ... Cissna’s job was in jeopardy last month as the agency coped with a surge of migrants crossing the border and a new caravan assembling. But Republicans including Sen. Chuck Grassley of Iowa went to bat for Cissna, and he did not leave with former Secretary of Homeland Security Kirstjen Nielsen.