Wouldn’t most colleges just consider transfer courses as passed or not passed in terms of calculating GPA for their own purposes?
Of course, if the student later applies to graduate or professional school, the conversion of French university grades for the purpose of such applications can matter for that purpose.
In terms of the French language, the Sciences Po part of the program requires French language course work, unless the student already knows French to the (CEFRL) B2 level or higher (in which case the student can choose another language to study): https://sciencespo.berkeley.edu/academics/sciencespo