I would say she did not; in fact, I would argue that the opposite is true in some ways. Wheatley's poetry establishes and sustains a specifically American identity for herself and contributes as well to the generic American narrative in a manner that has probably not been fully recognized.
Wheatley's most famous poem is "On Being Brought from Africa to America." Admittedly, her wording appears to demean people of African descent by referring to her own soul as "benighted" before she became a Christian. This, however, establishes the question of "enlightenment" as one of religion, not race. The poem is principally an answer to those who would claim that her race is inferior. Though in a genuinely enlightened world (which the eighteenth-century was on its way to becoming at the time), religion shouldn't matter, either, Wheatley still is expressing the primal American concept that those who come to the New World are given advantages not possible in the Old. There is, of course, an enormous gulf between those who came to America willingly and those brought there in chains. And in an enlightened world, no one should have to plead for others to accept them. But Wheatley focuses only on what she regards as the benefit of this forced immigration. At the time, her poetic options were obviously constricted by what would have been acceptable to the white establishment. But her main point can still be seen to fit into the overall American narrative; it is the echt American saga of success in the New World to which she is alluding and contributing as well.
Few Americans know that Wheatley, in her lines penned to Washington, was the one who probably first used the term "Columbia" to designate America. This, too, marks her as an archetypal purveyor of the American mythos. In retrospect, it is tragically ironic that the Revolution did not free the enslaved people. Though we may question Wheatley's decisions in expressing confidence that the oppressive system of the time would change, her identity as an African American (or simply an American) is confirmed in her poetry.