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I was in the United States 16 months ago when an Egyptian national popular uprising forced Hosni Mubarak to quit the presidency. And I was in the United States again this week when Mohammad Mursi was elected as the new Egyptian president. Then and now, Americans remain unsure about how to react to the popular revolutions that felled their longtime autocratic Arab allies, who in most cases were replaced by more legitimate, Islamist-led governments. At the same time, though, Americans – who helped to define the modern revolutionary and democratic era in the 18th century – instinctively tend to support national populist revolutions that create government systems based on the consent of the governed and democratic electoral pluralism. When Arabs carry out these revolutionary and...