Re: And to those Brits who celebrate Thanksgiving:
" We used to have Harvest Festival when I was a kid, not sure if it still goes on."
My neighbour's son is at a UK Catholic secondary school. IIRC he has to take a tin of something for a collection for the needy about that time of year. Presumably the ongoing legal requirement for a religious assembly allows the school to dragoon all their pupils*** into a Christian Harvest festival service.
I would be surprised if the CofE churches don't still make such collections for display by the altar - although probably much diminished. The Waitrose food bank basket probably outdoes them all year round. Today it was starting to overflow with boxes of mince pies and biscuits.
"We plough the fields and sca-tter the good seed on the land". Enough childhood repetition makes permanent memories even for atheists.
*** I wonder if atheists are recognised exceptions these days. That word wasn't even part of the vocabulary in my 1960s non-denominational secondary school. Assembly separation was limited to RC and Jews. Everyone else was basically in the set "CofE" - including the various brands of non-conformists and one Mormon.