Yes, of course, you’re right, the information is already there ! I’m confusing between “by category” and “by image details”, that's stupid of me.
And my question wasn’t clear anyway I’m afraid. To be more precise, the category labels (mostly places) were what I expected to be automatically documented. Your answer helps me see things the right way, the catalog “by category” differs from “image details” and the latter is sufficient.
That said, using this “by category” feature is so handy in fact, with rapid searching, and you easily visualize your collection, it is so attractive that I consider labelling my photos by category as well, using the script or MP import feature to bring the places fields in the categories labels, regardless of the need for the keyword (I usually “keyword” the town actually, not the state or country, but I reckon it may be time to think about it afresh).
As for the mapping… well, at first sight, it seems useless to map the category label with the IPTC field, I can agree with you : no use giving back to the xmp what this imported file brought to the database in the first place ! But it may be useful for event or people which I know I haven't tagged very thoroughly, as well as for foreign places I would have incorrectly written and want to correct. Image Details would then appear to be the logical way, that's right, but the Category feature would be appropriate as well, maybe even simpler, as you would sometimes browse the catalog and detect errors. But maybe I am wrong and Image Details would be a surer way to work through my database ?
Anyway, I discovered the new version 1.4 of the script Place finder labels, thanks a lot for that mapping, it works fine.
I go on discovering your soft, it really is a pleasure, and I must say the look of PSU suits me so much, very clean and stylish (it may not be the most important feature, ok, but it’s enjoyable to work with a nice soft, isn’t it).