When the 'Chief' brings the woman to the doctor, in town, his shotgun has a short barrel. Later, the same shotgun has a long barrel. It's not the same gun.
There are several scenes where there is considerable snow on the ground and then no snow and then snow again when it is supposedly the same day. During the scene where the characters are trapped in the bus there are alternating shots of snow falling and a clear night, even a shot of a full moon, within minutes of each other.
While it is true that Mennonites speak in a slightly different way from other modern Americans, their speech is not like the way the Mennonite characters speak. The most common error is the addition of French-root and Latinate words as most Mennonite speech is characterized by a reliance on German-root words.
The main goof of this movie is that although someone calls the birds 'crows' early in the movie, that person is corrected and told that they are ravens. No, most of the birds were in fact crows. The bird in question was a crow. There were very few actual ravens shown.
The cars seem to have the old type Pennsylvania license plate. However they are on the front of the cars. PA doesn't use front license plates.
Oskar says they are not Amish, but are Mennonite. They dress plain and paint the chrome on their cars black (Black Bumper Amish). They are a very conservative sect of Mennonite. Yet the girl, Gretchen, does not wear a bonnet or net on her head. This would not be. Mennonite women in a community this conservative would wear at least a lace net.
On emergency vehicles, the lettering is usually backwards so as to be read by a vehicle in front of it. The Bronco's "Emergency 911" is written standard. Of course, this town has cops in very loose jeans about to fall off, so maybe the nuances of lettering aren't a priority!
When Clyde is working on the bus, the fan blade is visible in the shroud, yet when the engine is cranking, and sound effects indicate it is turning over, the fan blade does not move.
Early in the film, after the farmer is killed in the barn, the Chief is called by dispatch to investigate. However, there is no one at the scene to have reported it, and he seems to accidentally stumble on the body.