Leaders of the world's most powerful economies are converging on Hamburg, Germany, for the annual Group of 20 meeting. The summit, as usual, will provide a venue to discuss issues of critical international importance. But setting this year's agenda apart are the divisions that lately have grabbed the world's attention thanks largely to U.S. President Donald Trump's "America First" policies on trade, climate and security. Competing forces are trying to rebalance the global order, pitting nationalists and globalists against each other. The fight to change, or preserve, the status quo will seep into all corners of the G-20 meeting, both during the main event July 7-8 and as world leaders meet one-on-one on the summit's sidelines....