What exactly does that mean? Is it literally just anybody they "believe" to be physically outside the US? Or non-US citizens?
According to the National Security Agency web site, Federal law and executive order define a United States person as any of the following:
a citizen of the United States
an alien lawfully admitted for permanent residence
an unincorporated association with a substantial number of members who are citizens of the U.S. or are aliens lawfully admitted for permanent residence
a corporation that is incorporated in the U.S.[1]