The Spanish dollar (the piece of eight) was officially made legal tender by an Act of Congress on February 9, 1793. It remained as legal tender in the US until it was demonetized on February 21, 1857.
...am I correct in thinking that your origininal question was about a copper coin? Although the maravedi was originally gold, then silver, the coin was produced in copper a good while before the coin act mentioned above. As I recall, that act specifically dealt with silver coins--not with copper ones. So I would say that a maravedi would not have circulated in the states much. Silver reales, on the other hand, are fairly common finds at old sites. I would imagine that if one unearthed a maravedi here on dry land it was probably a curiosity piece that was lost. There was already a good bit of copper circulating in the states due to state-issued copper pieces, imported British coins (that were the models for our own coppers in terms of composition, weight, size, etc.), and others.
These are just my off-the-cuff thoughts on the issue.
Badger:
I'd also venture a fairly safe guess that the circulating life in the Colonies of a maravedi coin was significantly shorter than the life of a piece of eight for at least three reasons: The more generally accepted preference of silver over anything but gold, the consistency of the silver content in the 'piece of eight' and the ability to 'split' the piece of eight into 'two bits' and 'four bit' pieces of acceptible metal (silver) content.
Don.....