Thanks Giving has nothing to do with patriotism. It's remembered in the US because those who had crossed the atlantic to these shores (pilgrims in specific) were thankful to be still alive and threw a party in celebration of the help they got from their neighbors.
As for what vegatarians eat it apparently is called TuFurkey.
And happy thanksgiving. Be thankful we aren't all dead from the crazy things we or someone else has done (I always say that).
Stephen