What is Domicile?
Domicile meaning Place where a person has his or her principal residence. The person must intend to keep that residence for the foreseeable future. The sponsor of an immigrant must have domicile in the United States before the visa can be issued. This generally means that the sponsor must be living in the United States. In certain circumstances, however, one can be considered to have a domicile while living temporarily living overseas.
reference: U.S. Visas – Glossary