Although it might be more cinematic, witches were never burned at the stake in New England. They were either hanged or pressed (by large rocks being placed upon them by villagers). Burnings of witches happened in England.
The character played by Tom Naylor is called "Bill Maitland" in the dialogue but shown as "Tom Maitland" in the end credits.
No witches were burned in New England--or England. Pressing is used as a method of extracting a plea, not a punishment or a sentence.
When Richard Barlow starts to go down the cellar stairs there is a wire, possibly to power his flashlight, clearly visible just behind him to his left.
At about 41:30 - When the policeman leafs through the "Treatise on Devil Worship" the pages are all blank.
When they are waiting in the cemetery for the clock to strike 13, the clock actually strikes 14 times.
When Bill Maitland speaks to the garage attendant, the passenger-side windshield of his car is missing. Perhaps it was removed because it was flat and the camera would have been reflected in it.
Patricia visits Whitewood on Candlemas, February 2. It is bitterly cold in New England at that time of year, but there is no snow on the ground.
With the exception of Nan's boyfriend and the gas station attendant, all of the "Americans" speak with British accents.