I’m thinking of a quick trip 8 or 9 days to experience Christmas markets and festivities between Thanksgiving and Christmas. I like art, afternoon tea, cathedrals and evensong. Theater and or Christmas markets. I love cities decorated with Christmas lights.
You might enjoy "Christmas at the Botanics" in Edinburgh, complete with the lit trail a bit like Kew Gardens in London.
Edinburgh Christmas Market starts the day after Thanksgiving- https://christmasmarkets.io/uk/edinburgh-christmas-market/
Also keep an eye on the St Giles Cathedral website a lot closer to the time- they are bound to be doing special things (although maybe closer to Christmas than Thanksgiving)- https://www.stgilescathedral.org.uk/
For evensong try St Mary's Episcopal Cathedral- https://www.cathedral.net/
Glasgow also has a Christmas market at St Enoch's and a Christmas Fair at George Square- including a ferris wheel and ice skating. George Square, especially, is always very festive- or was before the big C- https://christmasmarketsineurope.com/glasgow-christmas-markets/
In Edinburgh for theatre see the various pantomimes which are happening- https://www.whatsoninedinburgh.co.uk/events/pantomime/
Likewise for Glasgow- https://www.whatsonglasgow.co.uk/events/pantomime/
Great suggestions but I woke up this morning and decided to go to Germany instead for Christmas markets. Booked my flights. Done and dusted! Now to decide on my itinerary and book hotels.