SUMMARY
It exists several IPTC location fields with the same semantic. 

iptc-core:location (legacy) and iptc-extention:sublocation
adobe-photoshop:city and iptc-extension:city
adobe-photoshop:state and iptc-extension:provincestate
adobe-photoshop:country and iptc-extension:countryname

There are also some others location fields such as those from Darwin Core with equivalent meaning (including a field "county" I just discovered !) but this schema is probably not much used.

The request is about to add the same capability to set the mapping (to read and to write) of these fields with country, state, city, sublocation as it is already allowed for caption, title, tag, color label and rating.