Pretty sure IQ has no relevance in one's competence at chess (except at the highest level maybe, but this is speculative).
It's reasonable to assume that if one's ability to learn is not impaired by mental retardation (which would be the only way in which IQ could limit one's ability), then one can easily improve from a theoretical 0 (which is where everyone starts since no one's born knowing chess) up to 1800 and beyond. Children learn faster than older folks, but it's feasible to anyone.
It's something one learns over time. It's a bit of a complex skillset so it mainly depends on the amount of effort you're willing to invest.
Chess isn't intrinsically difficult... Once one has a grip on basic patterns it's simple. Everything else is cumulative. It's just a lot to practice, learn and assimilate.
Well said!
Thank you kkl10