That's why I'm curious as to how a culture that converts to Judaism does so. Do they reject all the cultural aspects the are used to in favor of Jewish culture or do they attempt to merge the two? And how do more orthodox followers view such mergings?
Santeria is an example of an extreme form of religious merging through culture. It is basically African animism with a Catholic shell. I personally have no problem with such a fusion but many Christians find it not only barbaric but sacriligious as well. To me it is no different than when the Northern European people were converted to Christianity and continued to follow their age old traditions with new Christian names.
Cultures don't convert to Judaism: individuals do. If I understand correctly, I think what you're talking about is how and to what degree Jewish culture maintains its boundaries while living amongst other cultures.
There is considerable cultural syncretism between Jewish and surrounding cultures in terms of language, styles of casual literature, cooking, dress, music, and suchlike. Theological or religious syncretism is much more tightly controlled. There is such syncretism, of course-- Jewish liturgy and Jewish mysticism have both syncretized elements from various other traditions-- but generally speaking, elements taken from other religions are heavily redacted and reshaped to come more in line with theology acceptable to Judaism.
One could not have, for example, a Jewish version of Santeria. That kind of theology is fundamentally incompatible with Judaism, its ritual practices also deeply incompatible. There used to be, in the late 1960s, a fringe group calling themselves HinJews, which were attempting fuse Judaism and Hinduism: they were utterly rejected by the main stream, and mostly politely rejected even by the left-wing fringes. Likewise, the small fringe group calling themselves JeWiccans are having about the same success, and it comes as no surprise to any.
However, some JuBus (Jews syncretizing Buddhism into their practice, a largish fringe group) are managing to stay within the bounds of acceptability, by being careful to Judaize the philosophy and practices they import, and being equally careful to reject any kinds of folk Buddhist practice that cross the lines into
avodah zarah (prohibited worship, which is not merely heretical, but is beyond the pale). They walk a fine line, but they have shown it can be done; though there are also a number of JuBus who are not so careful, and their practices are unacceptable.
The lines between what is borderline heretical and actually heretical in Judaism can sometimes be fine lines, and there is considerable room in the Jewish world and tradition for debate and stretching of the boundaries to some degree; but what is
avodah zarah is usually fairly clear cut, and there is little tolerance given to attempts to fuse Judaism with what is truly incompatible, theologically.
