Your comment about the SE being a location of good riding can be a bit distorted. The map above doesn't just make the Appalachians "appear" to be further north than you think...they ARE further north. From my home in mid-eastern Tennessee, I'm probably 100 miles closer to southern Ontario than I am to northern Florida. Yes, I know I can go in a slightly different direction and go more than twice as far northward without leaving the U.S., but I'm just trying to put things in perspective. Compared to going all the way to Maine or to Minnesota or the like, I'm definitely in the southeast. But you don't see that so much on that map.
I'm spoiled by the close proximity of excellent riding. I don't know if this is historically correct, but I theorize that our Appalachian roads today started as game trails, then foot paths, horse trails, wagon roads, and finally modern roads...to a great extent, they still following the original game trails. If accurate, my gratitude to the little furry creatures that created all of those curvy little paths is immense.
Again, this is just my theory, but the roads through the mountains of the west tend to have been created recently enough to be a victim of road builders' desire to make roads more direct. Instead of following the lay of the land, the roads plow straight ahead. It may be more efficient for road users, but it's a lot less interesting to me. I absolutely agree that the scenery can be spectacular and there are wonderful sections of road. But for the most part, they just aren't as curvy and tight as what you'll routinely find in the Appalachians.
Feel free to disagree...your opinion will be just as valuable as mine.