Difficult negotiations go to the brink for a reason, and that dynamic is being revealed on numerous fronts. U.S. and Chinese trade negotiators are meeting this week, but the Americans are downplaying prospects while raising new headaches. The U.S. Navy is steaming through the South China Sea, and Washington is countering even the venue for a possible mid-March summit by Donald Trump and Xin Jinping. In transatlantic trade negotiations, the U.S. is accusing the EU of bad faith and awaits a Commerce Department report on automobile imports it will then use to threaten tariffs on European luxury makes. There will also be a fight over digital services taxes as policy differences are highlighted. Domestically, a comprehensive agreement is possi...