Many expats that want to move back to the US also want to bring home their foreign spouse. As part of the visa process, proof of domicile can be hard to prove especially if the US citizen has totally uprooted from the US for a long time. This article I found helps people find out what they can do to get Proof of Domicile. http://www.lovevisalife.com/2018/05/proof-of-domicile/