Mexican President Felipe Calderon addresses a joint meeting of the U.S. Congress on Thursday. Chip Somodevilla/Getty Images hide caption

itoggle caption Chip Somodevilla/Getty Images

President Obama walks with Afghan President Hamid Karzai at the presidential palace in Kabul on March 28. In recent comments, Karzai has blamed the West for many of his troubles, causing concern in Washington. Charles Dharapak/AP hide caption

itoggle caption Charles Dharapak/AP