Green is in the northwest corner of Wisconsin.
Yellow is honestly a terrible color choice for this map, because the pronunciation isn't truly regional. I think it's clustered along the edges of a few different red areas, mostly on the east coast and some Southern areas.
I actually think the author's note about it being a merging of pronunciation makes sense, because I was raised in a transitional Southern dialect but my parents both have an east Midland dialect
Oh hey, I was in a similar boat. I was such a big fan of Skillet that I got them to sign a skillet at one of those Christian music festivals. I listened to them again recently, those lyrics are definitely propaganda.