I always thought the plan was we give them pieces of paper for their stuff. Then if we ever needed to we could say those pieces of paper(or bits in a computer) are no longer worth anything unless you're a citizen. But I had a bunch of gift certificates for ChiChis when they went out of business, and I have been jaded to this sort of thing ever since.
Why on earth would we ever do that? That's a nonsensical proposal that would immediately make an immense amount of people poor (while also being hostile to so-called foreigners for no reason)
Though I would like to amend my nonsense from "a citizen" to "actually in the country" I am imagining cutting off foreign governments and oligarchs, not humans that are actually living here.
Basically, if there was a bad war or something, and we needed to cut ties with most of the world. It's better to be left with the goods than the cash. Because cash has no intrinsic value.