What does that have to do with giving thanks? Aside from the fact that it sounds like complete bollocks this story.
What does ham have to do with Easter? Or macaroni salad with the American Independence Day?
I'm not sure I follow your frame of view that a traditional food item must unlock the key to a given ritualistic holiday there, Martin. All you need to know is that Thanksgiving is the greatest holiday on the American calendar.
Unlike Christmas, which is absurdly commercialized, there isn't some social pressure to buy more crap, send cards, and the like. Unlike Easter, there aren't the heavy religious overtones that will exclude one faith and not the other.
The purpose is to get people together, have a couple of days off work, drink, eat, and be thankful for what you've got. It's brilliant. I have yet to experience a holiday the world over, in different faiths, with a better message and the inclusive, low-stress enjoyment that Thanksgiving has.
I'm actually a bit surprised that Americans haven't completely ruined it yet with religious implications, required gift giving as a commercial opportunity, etc. After all, America is the country of excess where advertising is all about telling us to want more -- how un-American is it to take a couple days off of that and say, "Let's be thankful for all the people, the virtues of life, and the relative abundance of all the crap we already have."
Canadians loved it so much they created their own and celebrated it over a month ago.
I'm pretty sure Turducken is the worst idea ever. That combination just disgusts me. Of course it had to be invented by some fat guy from Louisiana.
So a turkey, a duck, and a hen walk into a bar...