is "the two of us" a partitive construction or something else?

it seems to carry the implication that "the two" is equivalent to "us", which is not typical of partitives (some claim that a partitive must refer to a proper subset of a set of things)

@alyssa something else i think; it’s saying essentially “the two which form us”, “the two that we are”; in this sense i think the usage of “of” is more attributive (qualifying which two), like in “the united states of america”

@Lady yeah, i interpret it the same way, but i'm unsure of other cases where "the X of Y" has that function in english. i'm not sure your "united states of america" example fits; would you not consider that a genitive?