[W]ith the “no” vote in Sunday’s Greek referendum on bailout terms posing the biggest challenge yet to decades of European integration, risks to the European project resulting from Germany’s rise as the Continent’s most powerful country are becoming clear. On Friday, Spanish antiausterity leader Pablo Iglesias urged his countrymen: “We don’t want to be a German colony.” On Sunday, after Greece’s result became clear, Italian populist Beppe Grillo said, “Now Merkel and bankers will have food for thought.” On Monday, Ms. Merkel flew to Paris for crisis talks amid signs the French government was resisting Berlin’s hard line on Greece....