Get the IRS to change your status to “foreign person” ie. not a US citizen or resident alien.
“26 CFR 301.6109-1 – Identifying numbers.
(g) Special rules for taxpayer identifying numbers issued to foreign persons
(i) Social security number. A social security number is generally identified in the records and database of the Internal Revenue Service as a number belonging to a U.S. citizen or resident alien individual. A person may establish a different status for the number by providing proof of foreign status with the Internal Revenue Service under such procedures as the Internal Revenue Service shall prescribe, including the use of a form as the Internal Revenue Service may specify. Upon accepting an individual as a nonresident alien individual, the Internal Revenue Service will assign this status to the individual’s social security number.”
If one is successful at acquiring a USA passport as a non-citizen national, one can write to request an authenticated copy of the application and all paperwork submitted with it. That should serve as proof of foreign status.