President Trump will host Britain’s King Charles III for a state visit at the White House on Monday, as tensions remain high on multiple fronts. Washington is still reeling from Saturday’s attack at the White House Correspondents’ Dinner. A gunman, who is in custody, targeted Mr. Trump and Cabinet officials, according to his manifesto. At the same time, anxiety is running high between the U.S. and the U.K. over Mr. Trump’s war in Iran. The two countries are longtime allies, but Mr. Trump has