"How often does it [Nov 22] fall on Thanksgiving?"

A better phrasing of the question would be "How often does Thanksgiving fall on November 22?" because November 22 is 'fixed' and Thanksgiving is not.

2012, 2018, 2029, 2035, 2040, 2046, 2057, 2063, 2068, 2074, 2085, 2091, 2096

When we look at those numbers we can easily see a pattern that will hold true until we once again re-adjust the calendar by having a double leap year--that is a leap year where there are TWO extra days added, but since that occurs only once every 10,000 years or so it need not affect this calculation.

The pattern is easily discernible by noting the years between the above dates. The pattern is such: 6,11,6,5,6,11,6,5,6,11,6,5 and so on. A very simple calculation when compared to "Who put the bomp in the bomp shu bomp shu bomp?"