Only if you ignore the earlier, Catholic manifestations of the feast, this blogger contends.
An interesting bit of trivia is that the first American Thanksgiving was actually celebrated on September 8, 1565 in St. Augustine, Florida. The Native Americans and Spanish settlers held a feast and the Holy Mass was offered. A second similar "Thanksgiving" celebration occurred on American soil on April 30, 1598 in Texas when Don Juan de Oñate declared a day of Thanksgiving to be commemorated by the Holy Sacrifice of the Mass.
The Catholic origins of Thanksgiving don’t stop there. Squanto, the beloved hero of Thanksgiving, was the Native American man who mediated between the Puritan Pilgrims and the Native Americans. Squanto had been enslaved by the English but he was freed by Spanish Franciscans. Squanto thus received baptism and became a Catholic. So it was a baptized Catholic Native American who orchestrated what became known as Thanksgiving.