I confess to a Falling Skies addiction. The end of this summer's season, though, left me skeptical. Short plot summary: Earth (or at least the United States, or perhaps the major military powers) invaded by space travelers coming for reasons not clear, these invaders kill adults and enslave children with the help of large aquatic earwigs. These space travelers are in a conflict with other space travelers, who have also become involved in the conflict on earth, or perhaps in North America.
The first invasion wrecked a lot of infrastructure, and almost all aircraft capable of flying, and somehow the resistance in the Boston area manages to cross the Connecticut, Hudson, Delaware, Susquehanna, Potomac and possibly the James rivers in order to get to Charleston.
The second set of space travelers are building some kind of beam weapon, and this weapon gets barged from Charleston to Boston, somehow avoiding a known strongpoint in New York City and detection from any robot fighters called "beamers". A decoy weapon gets loaded onto a train that is headed for Chicago, involving a rail crossing of at a minimum the Ohio River, plus possibly the Tennessee and Cumberland rivers, to credibly get near Chicago. There's apparently enough diesel fuel to move this train, which is either powered by contemporary six-axle diesels (the exterior shots) or at least one F unit (best evaluation of the interior shots, with an impossibly crowded cab). This train also evades interdiction until it gets near Chicago, and that interdiction may require the presence of a known spy.
Taken together, the show suggests the first set of invaders are technically advanced (capable of interstellar travel) yet not very bright. In addition to not being able to spot large moving objects or destroy all possible river crossings (collapsing a few rail tunnels would also work), their rationale for cleaning Earth up is one that would appeal to tree-huggers and the Blame America First crowd. Had they introduced some agents into the academy to prepare the grounds, they might have been hailed as secular saviors. Instead, they apparently arrived above the stratosphere prepared to take out any military opposition.