America’s unconventional oil boom continues to yield major benefits—economic and geostrategic. The latest evidence is OPEC’s decision on Thursday to defy expectations and maintain its current oil production target despite the steepest price decline since the 2008-2009 recession. The price of Brent crude, the global oil benchmark, plunged as a result to about $70 a barrel, continuing its decline from a peak of nearly $116 in June.

Not too many years ago the Organization of Petroleum Exporting Countries might have cut production...