If you're having trouble opening the link that Cape Chef recommended, try this one: holidays.bfn.org/thanksgiving.
-- no "www." (You may have to type the address in, rather than just clicking on the one in this message. I tested it, and had trouble with the shortcut.) It has a variety of information ranging from history of Thanksgiving to food and decoration items.
I vote with the folks who have told you that there are both regional and family traditions in what is eaten on Thanksgiving. (The US is too geographically, regiously and ethnically diverse to have very closely bound set of traditions for any holiday.)
Although Thanksgiving is one of our most widely observed holidays, it really began in its modern form in the 1930's. Before then, a Thanksgiving holiday was frequently declared, but it was kind of a one-off thing. As a secular holiday, and a relatively recent one, Thanksgiving tended to "borrow" traditional foods from whatever was locally available. SInce it occurs at the end of the harvest season in most areas of the US, what is locally available tends to be whatever is regionally being harvested. From there, each family develops its own recipes.