It's actually an interesting philosophical point.
Converting to Christianity has nothing to do with souls -- any being with the appropriate mental capacity could choose to convert. Converting involves:
1) belief in an intelligent being who exists outside our space/time continuum
2) belief that such a being takes an active interest in the goings-on in our universe, including on this planet
3) belief that such a being can manifest itself inside our universe in multiple forms that can communicate with each other and the being as a whole
4) belief that this has actually happened, and such a being has both artificially impregnated a woman and has a means to inject a link to itself into the consciousness of homo sapiens sapiens (and possibly others, but we don't know that).
5) belief that the resulting being who was born from the impregnated woman then began challenging people to treat the people and environment around them with equity and compassion, not only in physical action, but also in how they thought about said people and environment.
6) belief that said being was then hung on a crossbeam until dead (signs indicating that there was total heart failure)
7) belief that said being was then able to be resuscitated 3 days later and continue functioning in the human body for a time
8) belief that after this time, said being then was reunited with the part of the intelligent being who exists outside of our space/time continuum
9) belief that following this, permanent links to the consciousness of humans were made available to any who would choose to follow 5)
Pretty much everything else outside of this is window dressing, labels, supposition and tradition.
As such, an artificial intelligence could accept all those premises as true and choose to follow The Way, but would not expect a link to the Holy Spirit as it wouldn't be HSS. But then, if God exists and is omnipresent/omnipotent, there's nothing saying that such a sentient being as the AI *couldn't* be imbued with the Holy Spirit other than human elitism.
The concept of souls has changed a lot throughout human history, so assuming they exist, the exact definition of what they are is still up for grabs, as nobody's definitively figured it out yet. The words translated Soul in the biblical OT and NT are referencing the same "soul" but the concept is different. Early OT seems to equate heart and soul as making up the entirety of your consciousness, whereas by the later letters in the NT, the soul has fully taken on an identity as being the part of you that doesn't die when your body dies.
There are also people who profess to be Christians who believe in the creation of a new earth where all functioning organisms have a second chance at life -- which would imply they believe that every functioning organism has some part, call it a soul, that is separate from its molecular construction.
Oh yes, and the "convert" concept has to do with the linking of the human to the spirit of the external intelligent being -- kind of like converting a regular car to be semi-autonomous.