There is a rumor being perpetuated by some well-meaning individuals to show that Thanksgiving Day in America is linked to the Levitical Feasts and the various offerings. To support their idea, they cite scriptures such as Leviticus 3:17 and 7:12-15. So, are they correct in their assessment?
(1) Thanksgiving is NOT mentioned in Scripture as one of the Holy Days.
(2) Thanksgiving in the U.S. was originally a harvest festival celebrated by the Pilgrims (joined by some Native Americans) after their first harvest in the New World in 1621.
(3) Leviticus 3:17 and Lev 7:11-15 are all about PEACE offerings that have nothing to do with our national "Thanksgiving Day" in America. These passages weren't referring to any kind of holy day; they were discussing peace offerings to be done by the cohanim for YHWH's people.
(4) If Thanksgiving WERE a biblical feast, then the dinner on every Thanksgiving table today, would include ONLY "clean foods" instead of ham and white gravy with bacon bits, and Jell-O, etc.
(5) America, as a whole, does not follow any of the Biblical Feasts, much less, bother with offerings.
Many attempt to demonize Thanksgiving as being a "bad" holiday because "white man stole this land from the Natives" - but if these people knew world history, they would realize (1) that it happened and (2) that they need to deal with it; and that (3) it's petty of them to bash those of us who wish to THANK GOD for our bounties! Most of all, they need to start recognizing that "taking over other lands" has been going on since the beginning of time, right down through World Wars I and II and, it is still happening today by world terrorist groups such as ISIS....
Others attempt argue that "Thanksgiving is pagan" (especially many Hebrew Roots types who try to tell you that EVERYTHING is "pagan" including the name "Jesus" and the word "amen" and your preferred spelling of the English transliteration of the Hebrew spellings of the "Sacred Names"); yet, there is absolutely NO reason to believe it's "pagan" to set aside a day to honor and give thanks to our Creator! Unlike Christmas and Easter, Thanksgiving does not masquerade as a biblical "holy day." (For more, please see this Wikipedia article)
While it's a nice idea to believe that America's Thanksgiving Day is rooted in the Bible, the fact is, it is not. Our Thanksgiving Day in America has nothing whatsoever to do with what YHWH told Israel thousands of years ago. Thanksgiving Day in America started solely because our country was founded "under God" and our leaders decided to turn it into a national holiday.