Children born in the USA are US Citizens, even if they haven’t actually lived in the USA since they were young children. Citizens in this circumstance who wish as adults to move to the USA with their spouse and children face far different issues than do US Citizens who have lived all or the bulk of their lives in the USA.
First the “expatriate” citizen must secure a US passport, they often never needed before, particularly if they have also been a citizen of the country they’ve been living in, or have never traveled internationally. Then, although the process to bring their spouse and children as immigrants is essentially the same as any other spouse or child of a US Citizen, there are some key differences.
Often, the biggest hurdle is to meet the requirements of the affidavit of support, including qualifying, usually with liquid assets rather than income, or having a family member or close friend living in the USA, act as a qualified joint sponsor. Current income that will not continue from the same source once in the USA cannot be used to qualify. Another affidavit of support related issue unique to the expatriate citizen is showing sufficient evidence of their intention to establish or re-establish US domicile.
It is not enough to simply declare the desire to reside in the USA, file the necessary forms and pay the required fees, even though, intuitively, it would seem that would be plenty of evidence of intent. In reality, the US Citizen usually need to do things like open a US bank account, file US Federal Income Tax Returns going back at least three years, even if their foreign income was entirely exempt from US taxes. They also need to show evidence they’ve at least started the process of arranging an actual domicile. Usually, this is going to require at least one short trip to the USA, before the affidavit of support stage of the process.
In a situation like this, the expatriate citizen’s children, are not already US Citizens, even though one parent is. The children must also go through the same immigrant visa process, that a US citizen’s step child would go through. However, once these children enter the USA with an immigrant visa and take up permanent resident with their now “resident” citizen parent, they DO become US Citizens automatically, and can simply apply for a US Passport. The immigrant spouse, on the other hand, is granted only Conditional Lawful Permanent Resident status if married less than two years when they enter the USA or full Lawful Permanent resident status if married more than two years at entry.
We seldom hear of expatriate citizens in this situation, even thinking about trying to manage the process themselves, as there are so many additional hoops to jump through, compared to resident citizen cases.