The sustained plunge in global oil prices has brought deep, unexpected shifts on the geopolitical landscape, with impacts felt in the Arctic and the Middle East, and in the fortunes of the American heartland and the future of the Russian-Chinese strategic alliance. A U.S.-engineered market truce has helped energy prices rebound slightly this month after flatlining in April, but analysts say reverberations will likely be felt for years to come as they chip away at the foundational international partnerships in the post-World War II era and create new alliances and rivalries. Analysts say there is no way the U.S. and...