The outlook for this week’s Summit of the Americas changed abruptly just three days before it was scheduled to start, when the White House announced that President Donald Trump was canceling his plans to attend the meeting in the Peruvian capital, along with a scheduled side trip to Colombia, due to the crisis in Syria. Trump’s presence at the summit, in what was meant to be his first visit to Latin America, would surely have monopolized the spotlight. Without Trump, the focus instead will be on the substance of the summit. Unless, that is, an even more dramatic arc unfolds. […]