After two years of falling prices, the effects have reverberated across the globe, fueling economic discontent in Venezuela, changing Russia’s economic and political calculations, and dampening Iranian leaders’ hopes of a financial windfall when sanctions linked to its nuclear program will be lifted next year. At a time of tension for U.S. international relations, cheap oil has dovetailed with some of the Obama administration’s foreign policy goals: pressuring Russian President Vladimir Putin, undermining the popularity of Venezuelan President Nicolás Maduro and tempering the prospects for Iranian oil revenue. At the same time, it is pouring cash […]