I'm not the expert, by any measure, on this topic... just found out about it recently (from Bob). But my understanding from what I've read is that the worms move very slowly, on the order of feet per year. The glaciers eliminated any worms that might have been here, and when the ice retreated, the worms to the south could then advance northward. But they can't migrate fast enough to keep up with the retreating glacier. But they've been introduced into various locations by man's activities, eg, moving soil during construction, shipping nursery products, fishing bait, etc, etc. Once introduced to a site, they'll slowly spread from there. That's why there isn't a problem yet in all areas, but there doesn't appear to be a way to get rid of them once they arrive, so they'll continue to slowly spread.
As far as the situation behind Bob's house goes, I'm sure there could be other factors at work too (I'll leave that for Dr Frelich or others to address more), but there's no doubt worms are present, and the conditions Lee has described are visible. Deer, to my knowledge, don't eat the duff layer out of existence, and that's what you see in the highly damaged areas. Most of the leaf litter is gone; the worms destroy the forest floor layer, leaving only the most recently fallen leaves, with mineral soil directly below them. If oaks are present, their leaves are among the least tasty and will be the last to be eaten. Since the duff layer is the primary rooting zone of plants, including tree seedlings, they're seriously affected when the duff is gone.
Bob has become familiar with the signs of worms' presence, and can now recognize them in various places, and points them out. Stream corridors are likely areas for worm damage due to the release of bait worms. And there's an interesting "mustard test" described by Lee that you can do to verify worm presence.... mix a little yellow mustard powder in a couple quarts or so of water and slowly pour it on suspect ground; if worms are there, they'll come right to the surface to escape the irritant. Bob and I did that at his location, so I could see it work, and it did. Several worms came right out of the ground, post haste. I have a short video clip of it.