You need to provide a lot more information about the cable and its application before anyone can answer that.
As to why the USA uses AWG (numbering based on what looks like a strange/arbitrary logarithmic basis) and kcmil (cross-sectional area in square inches subject to other strange choices) that is just historical practice. Or hysterical in some cases.
The rest of the world, including the UK that originated the "modern" imperial inch-based system back in Henry VIII's day (he imposed gov standards and enforced them, but the actual origins go back as far as Roman times), have moved on the SI (metric) units with cable size in square mm.