Another point that young-age creationists would raise is the idea of the universal Fall. Creationists (like me) believe that human sin altered creation so that now "the whole creation has been groaning" (Rom. 8:22). That groaning came from the curse placed on creation because of Adam's sin. So if there is intelligent life on another planet, then that would seem to be part of the creation that is groaning, which means they've also been cursed because of human sin. That seems unfair.
We could also look at the passages of the New Testament that emphasize that Christ died once for sin (I Pet. 3:18, Heb. 9:28, Rom. 6:10), which is taken to imply that there would be no redemption available to intelligent life on other planets, since Christ died here and not there. Otherwise, He would have died twice, and that's not what the Bible says. This flows into the exclusivity claim of Christianity: Christ is the only way to God. Religious pluralism is false; therefore, there can be no alien Jesus, because that would be a second way to God.
This is a very outre debate. I have no stake in the answer. The question is purely speculative. And I have no opinion regarding the existence of other physical lifeforms elsewhere in the universe. If they exist, they too are the product of divine creation.
The question holds some hypothetical significance because you have Christians who imagine that this scenario would falsify the Christian faith.
i) In my opinion, the fall directly impacts the human condition and the angelic order. Angels are not alive in the biological sense. Strictly speaking, the "universe" denotes the physical cosmos. Angels are not a part of the universe, although they are able to interface with the universe.
ii) I think the basic error is hermeneutical: overextending passages whose intended scope concerns life on earth (or fallen angels). I don't think Biblical language speaks to the issue of extraterrestrials one way or the other. It has a terrestrial orientation. Not "universal" in the cosmic sense.
iii) If there is intelligent life elsewhere in the universe, they didn't fall in Adam. Adam wasn't their progenitor or federal head.
iv) In principle, I don't think Biblical language precludes the Son from becoming incarnate at more than one time or place to redeem fallen aliens, if such exist. For the intended range of reference concerns the unrepeatability of the Incarnation with respect to God becoming human (more precisely, the Son assuming a human nature) to redeem fallen humans. In context, he died once for all time for human sinners. It's unique in that regard. The status of aliens falls outside the purview of that discussion.
v) Christ is the only way to God because humans are sinners who require a mediator. A redeemer. Unfallen aliens don't require a mediator or redeemer.
In an E.T. context, there's still the same God, the same Trinity, the same eternal Son. That is universal, in the cosmic sense–or even a multiverse.