Klatch is a mixture of foreign places. They do have the foreign legion, but that's, i think, the only French reference. There's lots of arabia in there (particularly the place names and the stuff in Sourcery, along with the invention of algebra, zero and astronomy), but they also gave AM curries and they have jungles (containing a fountain of youth and various lost kingdoms) which suggest to me india and africa or south america.
Ephebe and Tsort are both remniscent of ancient Greek states with their culture and war history.... particularly the conflict Rincewind found himself in in Eric.
Llamedos, judging from the accent and druid culture, seems to be a bit Welsh.
Omnia... well I can't think of a country, but the Citadel is a bit Vatican, so the nearest thing would be the roman empire, but Omnians don't seem to be very roman to me.
Djelibeybi is, of course, ancient egypt with the knobs turned up.
The counterweight continent has the great wall, forbidden palace, fireworks and printing of China, with a little bit of Japan thrown in.
Genuan's certainly speak a language that is a little bit french, and they have the cooking to match, but they also have crocodiles, swamps and Voodoo. I think there's some ex-french city in America (New Orleans?) that is the closest match.
Uberwald is fairly eastern Europian. There really was a Diet of Bugs in some country in the area, and the Vampires and geography of the area are certainly right, along with Chekov's three sisters.
AM is based on lots of cities, I believe. The shape of the river and the Isle of Gods/Dogs do suggest London, but the strong presence of the University and the City walls are more like a University town such as York. I understand a few other cities throughout Europe (there's the italian Medici connection for example) and America have good claims for being AM.... but so do a few fantasy ones. I think Terry's said that it isn't anywhere else, its Ankh Morpork.
There are lots of parralells between places on the disc and the real world but it probably worth bearing in mind what Terry said at the start of TLC.... EcksEcksEcksEcks isn't australia, its just a place that happens to be a bit australian.
phew
any other places you were wondering about?
rob