Under Executive Order 11935, only United States citizens and nationals may be appointed to competitive service Federal jobs. In rare cases, agencies may hire certain non-citizens when there are no qualified U.S. citizens available, unless the appointment is prohibited by statute. https://www.usajobs.gov/help/working-in-government/non-citizens/
DESIRED GEOGRAPHIC LOCATION
For example if you are pursuing a GS-12, you must have one year of specialized experience equivalent to a GS-11.