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). Typically, in order to claim US domicile, the Affidavit of Support sponsor must be residing in the United States.A declaration is a simple statement that you intend in good faith to return to the United States to resume your domicile. This guide will explain how to prove domicile when filling out Form I-864 ("Affidavit of Support"). Consular processing support without the high price tag. There are five stages for application submission. 1.