Although the nationwide average for a gallon of regular gasoline remains above $2, it’s fairly well below that level in some parts of the country—such as at this station in Dellwood, Mo., earlier this week. Photo: Getty Images Gas prices appear headed below a nationwide average of $2 a gallon in coming days, extending one of the swiftest declines in decades and delivering a growing windfall to American consumers. The plunge is rippling through the U.S. economy in ways both familiar and unpredictable. Restaurants and bars are seeing their best sales growth in years. Americans are driving more—and buying bigger cars and trucks . Consumer confidence is sitting at an 11-year high , with lower-income households showing the biggest improvement. And some households are using the savings at the pump to get caught up on debts. But the drop in oil prices is also testing the […]