Can cdiff cause alterations in mental status?

Indirectly: Diarrhea from C diff infection may cause dehydration and electrolyte imbalance that may affect mental status.

If severe enough: C diff colitis can result in sepsis, which can manifest as alterations in mental status. C diff colitis causing sepsis is life threatening. The current definition of sepsis is called qSOFA. You get 1 point each for low blood pressure, high respiratory rate, or altered mental status. A score of 2 or more means you have sepsis. https://en.wikipedia.org/wiki/SOFA_score#Quick_SOFA_Score

Yes,: severe bacterial infections, particularly if sepsis occurs, can certainly cause mental status changes. Also, if the diarrhea is severe enough and untreated, both dehydration and anemia can results in altered mental status.