The USA certainly had a currency long before it had a central bank.
Wrong, the US had a central bank from the very beginning.
http://en.wikipedia.org/wiki/History_of_central_banking_in_the_United_States
GURPS Traveller material is some of the best-written of all Traveller versions.
From I what I have read here, I must disagree.
However, I have little interest in any further discussion along these lines; so much I have seen is incorrect, and I do not have the will to argue for the facts. I have now seen the face of sci-fi economics and I must say it is quite silly; at least it is not ST's "everything is free."