Factual error: When Tom has decided his scout group will have to go for the food and then his look for his son later, they are stood on a green. There is a war memorial dedicated to both World Wars, 1914 - 1918 and 1939 - 1945. That's got to be in Canada, as the USA didn't enter either war until later than those dates. (00:28:00)
Character mistake: Tom Mason makes references to smaller armies defeating larger ones, of which history is rife with examples. He cites the Scottish defeating 'the British' at the Battle of Stirling Bridge. 'The British' did not exist at that time. The Scots administered a beating against the English in the Scottish War of Independence, against the Earl of Surrey, under Edward I. Someone with his level of knowledge would know that.
Continuity mistake: When Tom starts shooting at the skitter in the food depot, the shots from his gun, the hits on the metal, and sound of ricochet are inconsistent with each other.
Revealing mistake: In the first scene, young people are removing scrap from a rooftop. The camera angle changes to look over the rescue team and back at the roof. In the distance, visible in the upper left of the screen, a Canadian flag is waving in the breeze. Also a short while later the camera looks back over the team away from the children, and the CN Tower appears to be in the background. Like many TV shows, Falling Skies was filmed in Canada, but the events are supposed to take place in Massachusetts, USA. (00:00:25 - 00:02:00)
Eight Hours - S1-E10
Character mistake: Pope tells Tom that the weapon he gives him is standard Army issue except it has a mech metal warhead. However the weapon he gives him is an RPG-7, a Soviet designed and built weapon.