as hatuey said, she can refuse and then not get credit for that "assignment".
That seems simple enough.
There is, of course, another way to look at the matter: the teacher could simply have wanted to emphasize that Spanish-speaking people in the region belong to Mexico, should be reciting the Mexican pledge of allegiance, and should be living in Mexico, not the U.S.
We probably lack sufficient information here to know.
Whether the teacher was spinning a liberal message or a conservative one, or was merely ignorantly insensitive to a regional hot-button issue, it would have been more academically appropriate and politically neutral for the assignment to have been to recite the Spanish pledge of allegiance.
Regardless, operating under the guise of an academic focus on "hispanic culture in the region" is not a valid excuse for the teacher's behavior.
The student was given an alternative assignment, one that appeared to require considerably more effort than reciting the Mexican pledge. More appropriate would have been to recite the Spanish pledge, considering that, linguistically speaking, Spain is the language foundation origination of "hispanic culture in the region".
Absent of any liberal or conservative oriented malice on the part of the teacher, the student should not have been punished for being more aware than her teacher.
Both liberals and conservatives would do well to be less political party-animalistic and more understanding in their response to these matters.