That's a great question, first of all! I believe there are absolutely common threads between all the world's religions (and cultures as well). It seems to me that we, in America in particular, have a tendency to over-exoticize (I just invented the word 'over-exoticize') the other, or perhaps I should say the OTHER!
By "over-exoticize" I mean that we have a tendency to be unduly shaken, amazed, romanced, enthralled, and taken aback by surface differences in cultural practice in a variety of areas. This in turn, leads us to the "slippery slope" of dehumanizing the other because we come to think of "them" as so different from "us" that we might as well be different species -- which, of course, makes it much easier, perhaps, to kill "them."
The easiet, most available, and most obvious example of this is this War on Terror (I know its not officially called that anymore) against various Islamic "terrorist" groups -- but that many can't help thinking of America's Christian war against Islam. Islam has always maintained that it comes out of the Judeo-Christian tradition and shows reverence for all of the prophets of those traditions including Jesus.
But Christianity and Judaism, however, do not, to the best of my knowledge, have very long traditions of embracing Islam as part of the "family. And so on and so forth.
Let me just close with this. The only way, in my view, that there coulld not be common threads in the world's various religions, would possibly be if the Earth were inhabited by multiple, different sentient species. But still, even if there were different, multiple sentient species living on the same Earth, presuming that "globalization" would occur at a similar level that it has historically, there would be cross-influence -- all would be constantly influenced, changed, and continuosly evolving...
I don't think there are many situations in which peoples (be they human or other sentients) could be living on the same planet and not generate "common threads" in religion and culture. I'll leave it there.