Washington Democrats and Republicans are questioning U.S. taxpayer aid to the Middle East amid anti-American riots in the region and the fatal attack on the U.S. Consulate in Benghazi, Libya.

One of the first attacks occurred Wednesday at the U.S. Embassy in Cairo, Egypt, a country that has received $1.6 billion in each of the past four years. Egypt has since 1979 been the second-largest recipient of U.S. aid, following Israel. Roughly $1.3 billion of that annual aid goes to Egypt's military, according to Congressional Research Service.

Four Americans were killed Wednesday in the Benghazi attack, including Ambassador Christopher Stevens.

Like Egypt, Libya was part of the political uprising that started in late 2010 known as Arab Spring in which residents in the Middle East brought down long-standing dictatorships. However, residents have struggled in the aftermath to bring democracy and political stability to the region.