Some argue that the American Thanksgiving holiday is a completely secular holiday and is therefore all inclusive. That assertion would seem to be a failure of considering the basic concept of the holiday, which is to "give thanks". Give thanks to whom, exactly? It seems more likely that the Calvinists established the tradition from which the modern observance is derived. In that case, they would very obviously be giving thanks to their god (their triune gods). This would seem to be the reason for establishing such a holiday.
It might be asserted that, "it's ok, because there's nothing wrong with giving thanks to God". Would one observe a Canaanite religious festival that is just about giving thanks? Or what about an Islamic festival? For what reason would we feel the need to worship the God of Israel with the ways that any other religion would worship its gods? This would very much seem to be contrary to what is presented in Dt 12:29-32.
The whole concept of trying to "purify" a holiday is not reasonable, and
is hardly different from the supposed Christianization of Halloween or
Christmas. At their core, they are still Celtic or Norse and Roman
pagan holidays, and claiming that they are now about worshiping a
man-god changes nothing (especially for us, being Torah-obedient).
It's certainly good to be thankful to the God of Israel for what He provides. However, we should not be adopting these non-Torah holidays and trying to worship our God in the way that other people established to worship their gods. We should be thankful according to the dictates of the Torah, not according to the dictates of other religious traditions.
Additionally, regarding the traditional turkey offering, and partially as an aside, we should reconsider our understanding of what is clean and unclean concerning birds:
Bird Species Identification: Is Chicken [or Turkey] Kosher?
