The episode originally aired in mid-September, which is closer to Canadian thanksgiving, than American. And the actor playing Kirk is Canadian.
But given the primary audience at the time, likely the intent was American thanksgiving. Kirk is depicted on the show as (most likely) being an American, so the crew "gets" a American special holiday meal. We know they also have Christmas parties. If Kirk had been Saudi, then perhaps the crew would have had a special meal on Eid Al-Adha.
I had a boss once who would give his employees a pizza party every year on Stevie Nick's birthday (May 26).