The role of the State Department is to oversee the U.S. Foreign Service. The U.S. Foreign Service is a part of the State Department and represents U.S. interests abroad through diplomatic missions. This includes embassies, consulates, and other diplomatic posts around the world. The Foreign Service officers are responsible for promoting peace, supporting prosperity, and protecting American citizens while advancing the foreign policy goals of the United States.
In contrast, developing the president's yearly budget proposal, including funding for foreign aid, falls under the purview of the Office of Management and Budget (OMB) and not the State Department. The Department of Homeland Security is a separate agency responsible for the security of the United States from threats within and outside the country. Developing an international trade agenda is typically handled by the Office of the United States Trade Representative (USTR) in coordination with the Department of Commerce and other agencies, not the State Department.