You will probably quickly notice that there is a lot of content presented here about the Hebrew language, various Rabbis and their works, quotes from the Tanakh and Talmud and the Zohar and The Sefer Yetzirah, etc. etc.
This is of course because Kabbalah is Jewish.
Kabbalah is not a repository of knowledge from ancient Egypt, it is not a version of Gnosticism, it doesn't encode secrets of the Eleusinian or Orphic rites, it doesn't presage the coming of Jesus, allude to the pantheons of other peoples, or any other number of fanciful attributions. It is, and has always been, a uniquely Jewish mystical system.
On top of that, not only is it a Jewish mystical system, it was developed by Jews who were (for the very most part) extremely devout adherents of Judaism.
Are there aspects of Kabbalah that can be traced to non-Jewish sources? Of course - it was not created in a vacuum. For the previous thousand years plus before the (public) development of Kabbalah around the mid 12th Century CE, Jews had been dispersed in lands dominated by Christian or Moslems, and for the 500 years or so before that had been ruled by Greeks, or Hellenized Syrians or the Romans in Palestine. The original paractitioners of Kabbalah were very highly educated scholars - mostly Rabbis - jurists, physicians, historians, mathemeticians and the like, and a relatively convincing case could be made that the original publicity of what was very obviously a conglomeration of extremely esoteric secrets was in reaction to the overt Aristotelianism of one of the most preeminent scholars and philosophers of the time, Maimonides. So yes, other cultures and ideas affected (positively and negatively) the development of the system. Nonetheless, Jewish it is.
However, Kabbalah is not Judaism. It bears a relationship to Judaism somewhat akin to that of Sufism to Islam (and indeed there are numerous instances of cross-influence between the two streams of mysticism), but there are aspects of some Kabbalistic teachings that I believe are irreconcilable with the teachings of normative Talmudic Judaism. It is only in more modern times, with the rise of the Hasidic movement (not to be confused with the much earlier Ashkenazi Hasidim), that a form of Kabbalah has truly entered a mainstream of the religion. Though - and this would probably be vehemently denied by adherents of the Hasidic movement - it is my impression that, had Judaism as a whole not desperately needed to show some sort of cohesion after the Messianic debacle of the Sabbateans in the 17th Century, the Hasidim would be regarded as nearly as schismatic.
I can't swear to that though, as not only do I not practice Judaism, if I did, it would absolutely not be the Hasidic variety. I don't do IHVH, and the overtly patriarchal and hereditary elitism of the movement is really not my thing.
So, a question could reasonably be asked, if I don't practice Judaism, what's with all this stressing of the Jewishness of Kabbalah? What gives?
The answer to that of course is because I am Jewish. Like really really Jewish. Like the my uncle was a dentist from Cleveland, two of my aunts were lawyers (one was a judge), my father was a surgeon, his father was a podiatrist, my mother a librarian, my mother's parents were both CPAs, my grandmother's brother made Kosher dills in his basement and all of their extended family who hadn't emigrated to the United States right before and right after WWI from what is now the Ukraine and Belarus, for the most part likely perished in the Holocaust kind of Jewish. I myself am an accountant, left-handed, bass player in a hardcore metal band (this is strangely common), devilishly handsome, with curly brown (now greying) hair. I am near-sighted, and slightly pronated. I share a side-view profile with John Stewart, my father bore a more-than-passing resemblance to Leonard Nimoy, his father looked like Albert Einstein, my cousin the mathmetician looks a lot like Groucho Marx minus the extreme eyebrows. I am lactose intolerant, have very defined opinions as to what is and what is not a bagel and even my mother would agree that I make better matzoh ball soup than she does. That kind of Jewish.
But, you might say, even with all that, you are no Jew, you do not practice Judaism. It's a religion not a race!
To that I say - go get yourself a copy of Maus by Art Spiegelman. Read it. Think about it.
Then read the very first page again.
Jews, whether we like it or not, are indeed a people, and have always been treated as such for good or ill. Even if completely secular or having converted (by choice or on pain of death - the Spanish Inquisition had a purpose after all). I would say this is almost even more so for the Jews that live in the US, as like my family, we pretty much all came from the same area of Central/Eastern Europe fleeing poverty and pogroms. If you don't know about it, look up the Pale of Settlement. (Think Fiddler on the Roof with less songs and more violence). To the point that, someone like me, who does not practice Judaism and is quite extremely clear that I find organized religion a moral abhorrence, was told by an acquaintance, whilst playing pinball at my favorite neighborhood watering hole, that no, people didn't refer to me as the Wizard (even though I not only look like one, I am one), but rather I am known as "the Jew".
So maybe it makes a sort of sense, that once I finally realized at a young age that - unlike the heroes of one of those fantasy stories about King Arthur and Merlin and the ancient magic of the druids and the Fey and elves and dragons, I would never suddenly find out that I was really secretly a royal prince, destined by my bloodline to have the magic in me the whole time - that I would end up studying a form of magick and mysticism that indeed does form a part of my heritage. At least until the Christians got their hands on it.
Ahh the vagaries of life...