Canada has a Thanksgiving as well.
Thanksgiving (Canada - Wikipedia)
From the above:
"Years later, French settlers, having crossed the ocean and arrived in Canada with explorer Samuel de Champlain, from 1604, also held feasts of thanks. They formed the Order of Good Cheer and held feasts with their First Nations neighbours, at which food was shared.
After the Seven Years' War ended in 1763, with New France handed over to the British, the citizens of Halifax held a special day of Thanksgiving. Thanksgiving days were observed beginning in 1799 but did not occur every year.
During and after the American Revolution, American refugees who remained loyal to Great Britain moved from the newly independent United States to Canada. They brought the customs and practices of the American Thanksgiving to Canada, such as the turkey, pumpkin, and squash."
So, it appears American Thanksgiving was being celebrated in some form during the America Revolution. I love Thanksgiving!