Ms. Noem’s demotion to become a “special envoy” for a new security initiative is the first Cabinet-level shakeup of Mr. Trump’s second term. The former South Dakota governor had drawn sharp criticism from Republicans in Congress over her leadership as well as her stewardship of taxpayer funding. Her ouster leaves the sprawling Department of Homeland Security in a leadership flux as it enters the fourth week of a funding shutdown – and stands alert for threats as the U.S. continues bombarding Iran.