This general prayer of thanksgiving has been adapted from the Book of Common Prayer and would fit well during a worship service on the Sunday after Thanksgiving.
Most gracious God, by whose knowledge the depths are broken up, and the clouds drop down the dew; we give to you sincere thanks and praise for the return of seed-time and harvest, for the increase of the ground and the gathering of its fruits, and for all the other blessings of your merciful providence bestowed upon this nation and people. We fervently ask that you would give us a just sense of these great mercies; such as may appear in our lives by a humble, holy, and obedient walking before you all our days. Through Jesus Christ, our Lord, to whom, with you and the Holy Spirit, be all glory and honor, world without end. Amen.
-adapted from the Book of Common Prayer