Late War of the Worlds thought: the screenwriter was faithful to the original novel in that the aliens are done in by germs - though we get a gratuitous scene of US soldiers bazooka-ing a sick and dying alien to death.
It seems that, historically and even in film, the US can't win a war unless a far more numerous ally has softened the enemy up beforehand. World War II? The Russians and Chinese respectively kept German and Japanese forces tied up while the Americans (and Canadians, and British) did the easy work. When the aliens invade, we'll have to rely on bacteria which not only outnumber us, but outweigh us by orders of magnitude. Good to know.