The contrast between Friday’s press conference in London by British Prime Minister David Cameron and Thursday’s White House remarks by President Obama could not have been starker. Mr. Cameron delivered a robust assessment of the scale of the Islamist threat to Great Britain and to the free world. He told journalists assembled at Downing Street that “what we are facing in Iraq now with ISIL (Islamic State) is a greater threat to our security than we have seen before.” While David Cameron appeared self-assured and determined in his approach, Barack Obama came across as a deer in the headlights, unable...