My wife and children were supposed to return from a visit to her family in Israel before the Passover holiday but they haven't come home. She texted me a whats message to say they are staying in Israel and everything is over. I am devastated. Our whole life as a family has always been in the states - house, business, kids's schooling etc. What can I do?

Bring Hague Convention child abduction proceedings against your wife, at the family court in Israel, for the prompt return of the children to the U.S.A.

Although your wife travelled from the USA to Israel with the children, your consent to their departure was within the context of a visit /vacation. You did not consent to them relocating to Israel permanently and, therefore, their retention by her, in Israel, after the planned return date is an act of passive child abduction ( ‘wrongful retention’).

Both the USA and Israel are bound by an international convention designed to prevent civil acts of child abduction. According to this, any disputes relating to the children are to be decided upon in the children's country of habitual residence, which in your case, is in the United States, and where their best interests can be ascertained. One parent is not entitled to effect a unilateral change in the children's country of habitual residence, as your wife is trying to do, and for which a legal remedy is available.
Abduction To Israel