The revolution in shale oil production in the United States has had a major impact on global energy markets, leading to the collapse of energy prices but also limiting their vulnerability to geopolitical instability. In an email interview, Meghan L. O’Sullivan, the Jeane Kirkpatrick professor of the practice of international affairs at Harvard University’s Kennedy School, where she directs the Geopolitics of Energy Project, and the recent author of “Windfall: How the New Energy Abundance Upends Global Politics and Strengthens America’s Power,” discusses what a rebalancing of supply and demand will mean for geopolitics going forward, if a supply gap is on the horizon, and how shale has boosted U.S. hard and soft power.

WPR: The significant oversupply of oil markets has cushioned oil prices from a lot of the geopolitical turmoil in the world over the past few years. With the markets rebalancing, do you foresee geopolitics having more of an impact on energy markets? ...