The Romans in the latter years of their empire used dragons as one of their legionary emblems. The Romans seemed to have gotten the motif from the Greeks and/or the near east:
http://en.wikipedia.org/wiki/European_dragon#Roman_dragonsDragons/serpents have always figured in the myths of just about every culture on earth, including that of the Jews, where the the Hebrew term
tehom, "the deep," at the opening of Genesis is cognate with
tiamat, the Mesopotamian she-dragon. I think I've got that right, but I'm just drawing from memory..
The dragon is, to the Christians, a symbol of the arch-satan and the dragon is a symbol of good luck and sovereignty to the Chinese, but another Chinese position has them being banished to watery realms by Shangdi, the Supreme Gd of the ancient, pre-Taoist Chinese religion.
I don't know of the connection between eastern and western dragons; there's been a lot of speculation as to where the influence goes, but I can only say that dragons are a universal meme in human consciousness.