PepsiCo and Coca-Cola both had weak showings in the place they call home. It could be a bad sign for the future.The second-quarter results are in for Coca-Cola (KO 2.02%) and PepsiCo (PEP 1.76%), two of the most important consumer staples makers on the planet. These giant soda companies witnessed similar weakness in one very important market. Here's a look at what happened and why investors need to worry a bit.PepsiCo took a harder hit than Coca-ColaBoth PepsiCo and Coca-Cola are U.S. companies. PepsiCo gen ...