The United States was questionably deemed to be like a corporation ten years before it became a body politic. In 1789 it became a body politic. Look at the date on the case. Listen to the sentence before your quote:
In that period the prosecution was grasping for something to compare the loosely associated state to, so they did - the Parliament of England. In that time frame the US was no longer Colonies but again they were not a constitutional republic either.The first exception was, 'that, at the time of the offence charged, the United States were not a body corporate known in law.' But the Court are of a different opinion.
Thanks though, that period is very interesting and I enjoyed you challenging my premise with that case.