Ask HN: Why would a government have created bitcoin?
Assuming your premise, I would proffer some version of 4), although not necessarily done by the U.S.The U.S. and its currency are toast -- in a decline, if not crash.Those who are relatively apolitical (not overly vested in any particular political system) with U.S.-based assets are going to want them denominated in some "neutral" form of tender.