But isn't He supposed to be omnipresent?
Not in his human form.
God "sent his son" to live as a human. Most assume that this human form is a manifestation of that God, that is that Jesus is part of God that lived on Earth.
Therefore on another planet its not too likely that this omnipresent God would visit it in earth-human form, might just scare the ,,, um Bejeesesus,, out of them. Then again if they, and we, are all made 'in his image' then they supposedly also would look like us, and therefore no problem with Jesus looking the same everywhere.
If God started life on other planets, and if the beloved by God intelligent species there was also made 'in his image', and thus looks like us, then one would assume that either: that planet's Adam made the same sin, and therefore if God wanted to save that world thousands of years later, he would have sent Jesus to them as well; or that Adam never sinned, and rejected Eve's offer of the apple. Perhaps alien Eve herself told the serpent to "go to hell", in which case there was no sin to absolve and thus all inhabitants, by Ham's own measure, are going to heaven. (they then, be better than we

)
Ham has no information upon which to base any assumption that the inhabitants of other planets were not either saved as well , or perhaps never required it in the first place. His only reference is a lack of reference to such things, in the Bible. So what? The Bible says nothing about electricity, internal combustion engines or computers either. Nor does the Bible even mention that stars are other Suns or that they have planets. Apparently He wanted us to discover these things on our own and thus it could be assumed that He wanted us to discover other worldly, God beloved, sentient beings on our own as well.