"were under atack"
"from who? is it the terrorists?"
"no it's not the terrorist, these guys come from somewere else"
"'somewere else?', like what Europe"
"NO, I don't think they came from Europe either"
That was actually pretty funny. Kind of shows the ignorance/arrogance of humanity.
But I think it is well known by the audience that the Tripods are alien in origin. There really is no need to say it out-right.
I thought it was really stupid how the teen wanted to join the fight despite that fact that the US Army was getting its ass handed to it. Just shows how.......smart todays kids are.
But I like the bellowing effect the Tripods had. It really made them seem more menacing.
EDIT: Come to think of it, I think that the book (and both of the movies) had a very important message: That we are not nearly as significant as we think we are. It is extremely arrogant to not even consider the possibility that there might be other intelligent life out there.