The Volkswagen brand, a stalwart in emerging markets and in Europe, has been hurting in the U.S. since 2013, facing stiff competition in the popular SUV segment. Volkswagen's strengths have been in sedans and hatchbacks, and the company's premium clean diesel TDI technology has helped check declines. But with the emission-cheating scandal hitting Volkswagen Group's small diesel engines, that advantage has been largely wiped out. This will hurt the brand's efforts to steer itself back to U.S. growth.