The construction " be it the US dollar, the Japanese yen or the euro" is not an appositive. True, if we removed "be it" we would have an appositive:
"--the US dollar, the Japanese yen, or the euro--" a construction whose content bears an identity relation with the noun phrase "major international currencies."
Ananja's utterance with "be it," however, is not an appositive. It is a reduced version of
Whether it be the U.S. dollar, the Japanese yen or the euro
...and is therefore a reduced adverbial clause. (Such constructions with be it contain two or more alternatives connected with or.)
This construction carries two special features: it uses the subjunctive be and also has an inversion of the verb be and the subject pronoun, in this case, it. Its use is often, though not always, formal. Here are some samples from a Google search:
1) Now, when the county makes a decision, be it right or wrong, that goes against the wishes of the township board, they are seen as the evil-doers who ignore the wishes of area residents.
2) He believed that laws designed to benefit one class of people at the expense of others "”(be they rich, or poor) "” represented a dangerous tendency toward arbitrary power and real injustice.
3) All it takes is one person with a vision -- be he rich or poor -- and the consumer
demand for a water-substitute or a street-substitute will be satisfied.
4) It's always fun when you surf around the net and find something that, be it now or later, can be very useful.
5) He is shouting, "Order, please," as folks clear the door. That's when he will toss
your dead critter on the grill -- be it a steak, a chicken breast or burger.
6) My kids had a bit of difficulty finding other kids to hang around with but with a bit of luck and effort they connected with someone (be it an American, a Uruguayan, or a German).
7) Someone, be it an American, a Dutchman, a Canadian, a Brit, a German -- someone made this poster.
All these constructions can be paraphrased with "whether (X) be...." For example, Sentence 3 could be paraphrased as
3a) All it takes is one person with a vision -- whether he be rich or poor -- and the consumer demand for a water-substitute or a street-substitute will be satisfied.
From these samples, it is obvious that writers are not always sure about the punctuation to use with such an aside. Examples 2 and 7 have especially odd punctuation. The usual punctuation is, however, commas or dashes before and after the expression.