If Indo-Europeans descended from Japheth then that would not make us Israelites, because Abram (Abraham) was descended from Sem (I'm using D-R version):
Genesis 5:31 And all the days of Lamech came to seven hundred and seventy-seven years, and he died. And Noe, when he was five hundred years old, begot Sem, Cham, and Japheth.
Genesis 11:10 These are the generations of Sem....
Genesis 11:26 And Thare lived seventy years, and begot Abram, and Nachor, and Aran.
I didn't say that Indo-Europeans descend from Japheth. I said they were descendants of the 12 tribes of Israel and thus, descended from Shem. The Vasconic, Kartvelian, Finno-Ugric, Turkic, Mongoloid, and Amerindian peoples descend from Japheth.
It is commonly assumed that Japheth gave rise to the Indo-Europeans but, in actuality he fathered some of the pre-Indo-European peoples of Europe, like the Vascons, Tartessians, Ionians, and Tyrrhenians who were later driven out and replaced by Shemites. Modern people in Europe who descend from Japheth are the Hungarians, Finns, Estonians, Lapps, Georgians, and possibly the Basque people of Spain.
The books I provided above go into detail using historical, archaeological, and Scriptural evidence on how the Lost Tribes became the modern Indo-European peoples.
The Jєωs would only descend from Shem or Abraham through Esau (Edom), while the Indo-Europeans descend from Shem and Abraham through Jacob (Israel). The Jєωs, however, descend from Canaan and Ham through Esau's Canaanite wives.