"The Canadian flag's supposed to be a symbol of power... it's a leaf! Yeah, don't mess with us or we'll dry up and blow away!"-Jeremy Hotz
Suppose that truth had simply dried up and blown away in the blasting wind of nuclear anxiety, cultural relativism,and psychological self-reflexiveness?
If Immermann ever dies or leaves, the settlement will dry up and blow away without the trading post to keep it going.
"Dry up and blow away" is a phrase that is meant to evoke the passage of time affecting something until it's entirely gone. The drying up portion of the image is meant to illustrate a loss of vitality, as living things shrivel and dry up when they reach the end of their lives. So a slightly different formulation of the phrase, "it looks like it could just dry up and blow away" describes something that is so weak, that it is on the brink of death.
In the first case, Jeremy Hotz is making a joke about the Canadian use of a leaf as a symbol. He implies that Canada is proclaiming that it is as weak as a leaf without a tree, something that is very likely to dry up and blow away. What he's saying is that the Canadian flag, and therefore Canada, doesn't project a frightening image.
The second case is saying that in the environment described, the truth suffered so much that it might as well have disappeared entirely. The simile at play is asking you to imagine the truth as a physical thing left out in a desert, a harsh sun of bad ideas grilling it until it is reduced to dust that blows away.
In the third case, Immermann is implied to be the lifeblood of the settlement. Without it, the settlement is expected to be incapable of surviving, again bringing us to the mental image of something drying up and blowing away.
I don't know the quote of Jeremy Hotz. Looks like the gag of a comedian. The first part (meant as a symbol of power) is taken out of thin air. Flags often show something that is characteristic of the country and Canada is rich in forests. So the symbol of a leaf is not a symbol of power, but simply saying something about the nature of the country. The second part is just a comedian's gag.
Dry up and blow away are phrasal verbs in English. These are verb constructions characteristic of English, and which are essential to understanding (especially casual) English and to sounding like a fluent, relaxed speaker. They consist of an ordinary verb, just as you would find in any language and as can be used on its own, plus one or more verb particles, which are almost always re-used adverbs or prepositions that originally mean something else.
Phrasal verbs in English have their own logic, and often mean very different and surprising things from what the bare verb part of the phrasal verb means. For example, "get" means something like take, accept, receive, or suffer; but "get on up" means rise or assume a standing position, with the "on" providing an additional nuance of familiarity and ease. "Get on up and dance!"
In this case, though, the verb particles are only adding to the basic meaning of the verbs, and not drastically changing them.
To dry means to lose or expel water. To dry up means to lose or expel water to a point of completion, which is a common application of "up" when used as a verb particle. To grow up, for example, means to achieve adulthood. So dry up means become completely dry.
To blow away means to be carried out by wind. Exactly where it goes? This doesn't say. It only says that it went further from the speaker.
Incidentally, the word "away" actually changes the normal valence of the verb "blow." This verb expresses wind-like motion, but by itself, it describes wind on its own, or wind causing movement to something else. "The wind blew away the leaves" is a sentence; but we could also say "the leaves blew away", which doesn't mention the wind, and reverses the perspective, even though the two sentences mean the same thing.
We'll dry up and blow away means that us, the leaves, will in the end expire of moisture and disappear.
Such is not only the fate of Canadians.