Share of McDonald's are down on Tuesday. Quarterly results missed forecasts. One key reason for the shortfall: U.S. stores under-performed. Earnings for the second quarter came in at $1.40 a share, that's four cents short of expectations. Sales rose 1% to a little over $7 billion, but sales at outlets open at least a year around the globe were roughly flat. Wall Street analysts were expecting same store sales to go up modestly, but that didn't happen. Comparable sales in the U.S. tumbled more than 1%, that was worse than expectations. On Monday, McDonald's publicly apologized for a food safety scandal in China. Local regulators closed down a meat supplier for McDonald's and KFC after TV footage showed meat passed expiration was mixed with fresh meat and factory workers were picking up meat from uncleaned factory floors. TheStreet's Julia Sun reports form Wall Street.