If you want to sponsor someone for a family-based green card, you need to provide proof of a U.S. domicile in your Affidavit of Support (Form I-864). Providing proof of domicile in the United States is critical for most people when submitting Form I864, Affidavit of Support.This guide will clarify what domicile is, how to establish it, and the documentation you need for proof of domicile. How Can I Prove U.S. Domicile? Proof of U.S. domicile is required for the I864. Learn examples of proof of domicile along with proof of domicile documents required. Typically, in order to claim US domicile, the Affidavit of Support sponsor must be residing in the United States. COMMONWEALTH of PENNSYLVANIA vs. GERALD J. SMITH, Defendant. Court Description: ORDER Denying 9 Motion for Evidentiary Hearing or Limited Discovery.