The type of chord progressions City of New Orleans aren't really that original, but they're different enough that under the current climate it might be possible for another artist, say Bob Dillan or whatever to argue that it uses elements that are entirely too similar to a song he wrote. There have been some really ridiculous lawsuits that have stuck so even though to me it feels ridiculous to do that, it's possible something similar has already happened. On the reverse, it's very possible that a modern songwriter would stumble into the same chord progression and instrumentation while also having a similar enough melody and articulation to Steve Goodman that he might have grounds to sue them even though there was no intentional copyright.
So, in order to avoid lawsuits, it's better to go with chord progressions that are so generic that nobody can claim them, or keep legal insurance and more lawyers on retainer. The industry seems to actually be going in that direction.
I'm not sure how prevalent copyright problems are with books. For example, you probably know that 50 Shades of Grey was originally Twilight fanfiction, and Stephanie Meyer doesn't seem to have gotten on their case for that.