An alien world would have its own Redeemer.
True, their Redeemer would be the Son of God, but the “natural” nature, I can’t say human nature, wouldn’t be ours.
The religion of our would might have most things in common with the relirgion of an alien world, but there might be differences. The two civilizaionts could have major differences.
We would not be obliged to have any allegiance to the alien world’s Redeemer any more than they would be obliged to have allegiance to Jesus. Each world will have its own salvation plan designed by God.