You would think that when bringing a korban todah [thanksgiving offering] in the Beis Hamikdash it would be a Turkey - but it's not...
The 3 basic opinions about celebrating Thanksgiving:
1] Absolutely forbidden as חקות עכו"ם [Rav Hutner in his Igros and also see Rav Menashe Klein in his Mishne Halachos 10/116].
2] Absolutely permitted [Rav Soloveitchik as reported in Nefesh HaRav and your parents and grandparents].
3] Permitted but not as a yearly celebration so as not to add on a new holiday to our calender [Yom Ha-atzmaut?]. [Rav Moshe in HIS Igros].
I am an American by birth and by mentality and appreciate the strong sentimental value Thanksgiving has for Americans but as a Jew I believe that the Jewish celebration of the holiday is a symptom of our assimilation into the general society. Chasidim in Williamsburg and New Square, for example, don't celebrate Thanksgiving. This is because they are simply less influenced [although not immune] by the gentiles around us.
On the other hand since it is only a symptom, it is better to focus on the root problem and dilemma, namely, how much should we be absorbed in the lifestyles and practices of the surrounding culture? Sports, entertainment, politics etc. etc.
A good topic of conversation for your family's thanksgiving dinner table....:-).
Bi-ahava and blessings for a hearty appetite and gobble gobble,
Me