Well, one reason that most of the top-ranked states mentioned are east of the Mississippi is that they were settled earlier and thus more populous, increasing the possibility that musicians and composers were born there--or left and felt nostalgic enough to write a song about them. California, while far west, was settled much earlier than the high plains and became more populous because it was reachable by sea. Kansas attracted settlers with free land early on.
And then some states are more colorful, with people with personality, joie de vivre, excitement about them. Towns with recording studios and thriving entertainment scenes attracted musicians first, and they wrote about what they knew. There's a reason Hoagy wrote "Manhattan Rag," not "Minott Rag."
Some names just scan better in rhyming lyrics or are more mellifluous, ("Alabamy Bound" sounds better than "Connecticut Bound." How do "Way Down Yonder in Wasilla," "New Jersey on My Mind," "I'm Comin' North Dakota," or "Rhode Island, Here I Come" grab you?