Have you considered jobs working in the federal government? There are several government agencies that offer worldwide employment. Of particular note and two that I have personal experience with are U.S. Agency for International Development (USAID) and U.S. Department of State. If you are interested in foreign aid and development work, then USAID would be the better option as they are primarily responsible for administering civilian foreign aid and development assistance. If you are more interested in foreign policy, then the State Department would be the better option.
The State Department has several internship and exchange programs for both high school and college student to allow them to experience first-hand U.S. foreign policy and diplomacy at work and explore various careers. Both State Department and USAID have a wealth of information on their websites regarding careers. I would highly encourage you to visit both of them and check out the various programs, jobs and benefits of each one. The Statement Department will probably offer more opportunities for travel as they operate 294 diplomatic missions across the world and USAID has missions in over 100 countries. Both also offer jobs in the business functions as well (i.e. management, human resources, finance, etc.).