The second-quarter sales performance at McDonald's  (MCD - Get Report) U.S. seems to have left a bad taste in the mouths of investors. 

Shares of McDonald's (MCD - Get Report)  were down as much as 4% in pre-market trading Tuesday as it reported that same-store sales in its largest market -- the United States -- rose 1.8% from the prior year, badly missing Wall Street forecasts for a 3.2% increase. Of particular concern, same-store sales growth cooled drastically from a 5.4% increase in the first-quarter. McDonald's promised it will add additional items to its all-day breakfast menu and enhance its core items this fall in a bid to jump-start sales.

The tepid results from the fast food giant reflects a broad slowdown in the restaurant space in the second-quarter at the hands of more cautious U.S. consumers, which also tripped up names such as Starbucks (SBUX - Get Report) and Dunkin' Brands Group (DNKN - Get Report) .  

"Traffic is still negative at McDonald's as the chain continues to wrestle with a Dollar Menu hangover, and prices of its premium items that are perhaps too high for perceived quality relative to chains such as Chick-fil-A or In 'N Out," wrote RBC restaurant analyst David Palmer in a note to clients ahead of McDonald's results.

Palmer, who slashed his second-quarter sales growth estimate for McDonald's to 2.5% from 3.5%, added that "finding the right value message remains a struggle, which is leading to negative traffic and varied sales trends around the country."
 
But considering McDonald's had been enjoying success with its all-day breakfast menu, and isn't exactly selling high-priced sirloin steak, its sales slowdown likely comes as a true shock to Wall Street.
 
The surprising performance in the U.S. overshadowed several positive areas for McDonald's. Earnings, adjusted for one-time items, came in at $1.45 a share, handily beating Wall Street estimates for $1.39 a share. And McDonald's bottom line continued to benefit from its cost savings efforts, mostly revolving around unloading company-owned stores to franchisees and cutting expenses at its headquarters.
 
Same-store sales at the company's International Lead segment rose 2.6%, in line with analyst estimates, due to momentum in the U.K., Canada and Australia. Sales gained 7.7% in the Foundational Markets segment, surpassing estimates for a 6.7% increase, as McDonald's said it experienced "very strong" demand in Japan.