My husband has dual nationality (American and Israeli), and wants our daughter,who was born in Israel , to have an American passport as well as an Israeli one. I only have Israeli nationality .We live in Israel . If we divorce, could it be disadvantageous for me if she has an American passport , and my husband wants to relocate to the States?

Having or not having foreign citizenship will not be the deciding factor in any custody or relocation battle that might develop between you and your husband concerning your mutual child . In order to relocate legally to the States with your daughter,should your marriage break down, your husband would either need your consent, or , if he objected, you would have to persuade a court that it was in the child's best interests to be in her father's custody, and be allowed to relocate abroad. 
Furthermore, only having one  passport and not two for the minor,  is no guarantee against against child abduction. Parents can abduct children on an Israeli passport only, if they so wish. Precautionary measures exist - whether your daughter has one or two passports.If your relationship with her father, breaks down, and you feel there is a risk of abduction, you could always apply for an order preventing your minor child leaving the country. If granted, the order would relate to any passport issued in her name,including a foreign one - subject to the details being supplied.