You answered your own question. They print it out of thin air. But they need to keep the drug trade going, and oil and gold, and they need to transfer funds between the 3, without it being obvious to all nations, how it's done.
correction, they don't even print it, they simply change a few bits of text in the computer and people accept that as a valid form of payment.
Yes, it's finger strokes across a keyboard. Not much more. But there is an accounting behind it. It's unaccountable though.