Amestris: It's already been established in one of csakuras's posts that Amestris is an English speaking nation (with many Germanic attributes). Amestris is a modern nation, having both electricity and automobiles. However, automobiles seem to be very recent since many towns in the countryside have yet to make roads and still use a horse-and-carriage.
The people are mostly likely Godless but there could have been a time where there was a predominant religion (from what I hear, there is an abandoned church in Central). Because the people are without religious convictions, this allows them to embrace alchemy while the Ishvalans detest it. However old alchemy is, it still seems to be in its exploration stage, used by the military as a weapon.
Aerugo: Not much is known of Aerugo at this time other than the fact that its south of Amestris. However, the term aerugo is used to describe the bright green rust that forms on bronze and other copper metals after it's exposed to air or acid (when I read this, I immediately thought of the Statue of Liberty in New York Harbor which is made of copper and has become infamous for it's green color).
Creta: Not much is know of Creta at this time other than the fact that its west of Amestris. It's most likely connected to Crete, an island off the coast [and is a part] of Greece.
Drachma: Dramcha is a country north of Amestris that has been on hostile terms with each other, seperated only by the Briggs Mountains, preventing a war from breaking out (for the time being anyways). Drachma is also the currency that was used in Greece from 1832 (when they regained independence from the Ottoman Empire) to 2001 when they accepted the Euro currency.
Xing: To the east of Amestris and past the Great Desert and the Xerxes ruins is Xing. Xing is often compared to China from the styles to the royal succession system. It's pretty much cut off from Amestris, excluding Xingese traders that venture using the sea route. It's unclear whether there is a widespread religion there but they do use alchemy (I believe it's called rentanjutsu). However, because Xing seems to be a much older country than Amestris, alchemy has been explored much more thoroughly and is mainly used for medical purposes.
Ishval/Isvhar/Ishbal/Ishbar/Ishbar Ishbar bo-bishbar/banana-fana-fo-fishbar-fi-fai-f
(big thanks to the factbook at www.fullmetal-alchemist.com)
Amestris seems, to me at least, like most European nations in the late 19th- early 20th century: modern, billigerant, and imperialist. I think when Amestris was first created, there were people with religious beliefs. But over time, the government probably encouraged athiesm which seems to be the case with most. Their annexing of Ishval only encourages this attitude.
I noticed, also, that Drachma and Creta are Greek influenced names. This is only a theory, but I believe that at one time these two nations could have been one country. But, due to Amestris' ambitions, they could have ceased the piece of land that connected them. Creta might have had a similar but different culture than Drachma and wouldn't have minded the split (much like the splitting of Yugoslavia into Serbia and Montenegro, Bosnia and Herzegovina, Croatia, Macedonia, and Slovenia). This could have prompt tensions between the two countries. However, because I don't have a good layaout of the countries bordering Amestris, this will only remain a theory.
Because of its meaning, I'm thinking that Aerugo was once a great nation but over the years has become a shell of its former self (much like the Spain by 1890).
We also know much about Ishval's similarities to the Middle East/India. The Ishvalites, on a whole, are peaceful people like many of the muslim peoples on the Mid East boot. However, there are some religious fanaticos, the most infamous is, of course, Scar
While researching some of this stuff, I found something interesting:
-March 17, 2004
Mitrovica, in Kosovo, experiences the worst ethnic violence in the regions since the 1999 war. At least 22 people are killed, and another 500 are injured. NATO sends in an extra 1,000 troops to restore order. The violence began after Serbs claimed a Serb teenager was the victim of a drive-by shooting and ethnic Albanians blamed Serbs for the drowning of several Albanian children.-
Of course, this happened three years after Arakawa-sensei first published FMA, but eerie coincidence, no?