U.S. oil drillers are finally beginning to buckle. For more than a year, American oil producers found a way to keep pumping despite a worldwide slide in crude prices. Like cartoon character Wile E. Coyote, U.S. drillers dashed off the cliff and somehow kept running in midair, maintaining volumes even as revenue plummeted. The companies’ latest projections, released in earnings reports in recent days, suggest gravity is finally taking hold.