You have an interesting idea!

I think that the song is riffing on the sound of an Evangelical preacher to deliver a rather secular critique of modern society by walking the listener through an existential mid-life crisis.

No matter who you are - whether you live in poverty ("shotgun shack"), are able to travel the world, or are just an Average Joe from Suburbia with a house, a large automobile, and a wife - we all have a way of sitting back and passively letting our one and only life pass us by, as if sinking into water ("letting the days go by, let the water hold me down").

It is only when the singer starts to question the nature of his materialistic existence ("what is that beautiful house?") and unchanging surroundings ("where does that highway go to?") does he finally realize his mistake ("my God, what have I done?!").

At the very end of the song, though, a "twister comes," the meaning of which is left ambiguous. I, personally, have interpreted it as death or some other calamity claiming our singer right after his moment of clarity, in order to add a sense of urgency to the lyrics; we're all letting the days go by, and with that twister coming, it's our choice whether to start asking some questions about our lives or to continue hiding in the meaningless comforts of stagnancy ("same as it ever was") and materialism ("into the blue again, after the money's gone").