Since the Obama recovery began in the second quarter of 2009, public and private projections of economic growth have consistently overestimated actual performance. Six years later, projections of prosperity being just around the corner have given way to a debate over whether the U.S. has fallen into “secular stagnation,” a fancy phrase for the chronic low growth seen in much of Europe.

This is just another in a long line of excuses. America’s historic ability to outperform Europe is well documented; we call it American exceptionalism....