I agreed to my wife visiting her family in the States, with our children after the birth of our youngest child, but now she refuses to come back home to Israel. Is this child abduction , if I consented to her visit in the first place ?

Yes - it is 'wrongful retention' , one of two possible acts of child abduction, under the 1980 Hague Convention on the Civil Aspects of Child Abduction, which binds both Israel and the U.S.A. Once your wife refuses to return the children beyond the time scale you consented to, then your consent ends, their continued stay is illegal, and an act of child abduction.