Can a std or sti cause a abnormal pap smear ?

Definitely yes: Abnormal pap smears are usually the result of cervical cells infected with a virus (human papilloma virus) that alters its machinery so it can produce more viruses.

Yes: Abnormal pap smear can indicate anything from infection, inflammation , precancerous situation to cancer. STI cause inflammation and can result in abnormal pap smear .