James 1:1 (NLT)
... I am writing to the "twelve tribes"- Jewish believers scattered abroad. ...
James is using an expression that represents the descendants of Jacob who became the biblical nation of Israel. This article (linked below) discusses the origins of the biblical nation of Israel:
(This name has also been appropriated by a cult originating in Tennessee. As fundamentalist, messianic Christians, they seem to have taken the New Testament language about the spiritual extension of Israel's role through Christians and applied it in a rather literal way. Nothing new in that... Sigh)