Well, Keith has said that they made a conscious effort with Eberron not to mimic real-world cultures with Eberron, and I think they mostly succeeded. For example, there's no "Asian" culture, though the gobins of Darguun use some Asian weapons and Chinese-style monasteries are common throughout Khorvaire. There are no Indian or Mesoamerican-style cultures, though I'd say there's the suggestion of Indian and Mesoamerican influences in the architecture and styles of Aerenal, Sarlona and Q'barra.
Of the parallels, most are in the human nations. Breland reminds me a bit of the United States, in that it's more democratic than the other monarchies, it's focused on industry, and it features big, cosmopolitan cities. Aundair could be a bit French, with its vineyards and classy vibe. Karrnath is very dark and military, which recalls Sparta, and also has some German qualities. Thrane's theocracy is a bit like any European monarchy dominated by the Roman Catholic Church. The Lhazaar Principalities are like a colder-weather version of the pirate-era Caribbean. The Valenar elves have some Middle-Eastern qualities, particularly their basic aesthetic. The Talenta halflings have some Mongolian and Native American influences. In general, tribal cultures are a more represented.
In general, though, I'd say places in Eberron are more defined by fantasy themes than historical parallels. There's never been a place that combines "primitive" nature worship with modern agriculture like the Eldeen Reaches, which is very clearly the "druid country." Droaam is definitely the result if "what if a motley collection of monsters attempted to assemble their own nation?" A nation of nations like the Mror Holds -- and its near-monopoly over precious metals and gems -- isn't going to happen in a world without dwarves. The seemingly benign dictatorship of Sarlona is not a totally new concept, but is too based on the psionic powers of its rulers to reflect anything historical.
So I guess that's a long way of saying "yes and no."
