While you could have a Jewish majority in "Jewtah", you can't stop non-Jews from coming in and while the majority may elect Jews to the political posts, you have the constitutional proscriptions against establishment of religion that will limit certain aspects of control, as the Mormons found out. Things like closing laws for Saturday (as opposed to Sunday) are certainly doable (until those laws and other religious based blue laws were struck down). Mandatory kosher rules for restaurants, forbidding the raising of swine or other non-kosher animals, not happening. IMHO one key for maintaining a Jewish majority in any state, is that its not terribly attractive as a destination. If you have rich farmlands, mineral wealth, etc you'll have a lot of non-Jewish settlers and others coming in , and there is no way to legally prevent it - discourage maybe but prevent no way. If there is some pull like that for settlers, you'll rather rapidly dilute the Jewish majority.
On top of those issues, the reality is that the Jews of "Jewtah" are not going to get any more support from the rest of the USA than the Mormons did. You have the "despised minority religion oppressing good Christians" meme just waiting to come out, the history of Mormon-federal interactions after the migration to Utah are replete with that.