Other mistake: Near the beginning of the movie, John's neighbor, Ed, is standing behind a wooden fence that is diagonal across the screen. The fence behind Ed is straighter. The angles of the fences indicate they are too close together - perpendicular sides of fences do not form a "V." Also, two BACK sides of fence are shown. Since Ed is within the fenced area, it is his (not John's) fence and the front ("good") side of the fence should be facing John's yard.
Factual error: The nuclear reactors on the US east coast, and European coasts, and their full fuel pools, would all have melted down and destroyed all habitable areas of the northern hemisphere, at the least.
Factual error: It would be virtually impossible to get from Atlanta, GA to Thule (Qaanaaq) Greenland in the time-span presented by the movie. The distance from Atlanta, GA to Ottawa, Ontario is approximately (direct) 1,200 miles which would take about 17 hours of driving, not counting breaks and side trips. The distance from Ottawa to Thule is approximately 2,200 miles. Plane type? Taking a guess, range of about 900 miles. Even with no fuel limitation, flying time approx 10 hours.