This week has seen a number of key events and crises in global politics that have made crystal clear once again the careening mess that is US foreign policy under the current administration. The Trump administration has no real overarching strategy—the argument that allies in Europe and elsewhere should bear more of the costs of their defense was not articulated as part of any coherent broader vision—and gutting of the diplomatic corps has left the US devoid of expertise and key actors to confront crises when they arise. First, there were two big stories around nuclear powers this week. The...