Offal-based dishes seem to be frequent on this list. Could it be some US or Anglo-Saxon prejudice against offal? Tongue, liver, tripe, etc are common in many regional European cuisines (not to mention Asian ones).
I've never seen any good writing on the subject but I've always found it curious that the US has sort of an arms length relationship with so many meats and almost complete rejection of offal (some liver and tongue and very rarely kidney or gizzard being the exceptions) as compared to, what seems like, the entire rest of the world.
If you look at old cook books from the US, say before 1950. There were more recipes for more parts of the animal. Offal was more common. Things like Sheeps Head, Intestine, Tongue, etc. were not rare. In the US' case it was really just a case of the United States becoming really wealthy (plus meat industry subsidies making meat cheap) that enough people started opting out of eating those things. 2-3 generations later and its disappeared.
My brother-in-law says that one may not sell hog maws in Oregon. He contrives to get some now and then from Pennsylvania, where he and my wife grew up. Even at farmers markets in central Pennsylvania, though, one must order ahead for them.
Probably go in on a hog with some 4H group. A lot of my coworkers in smalltown/semirural areas will raise pigs. Not sure if it would be a violation to see hog maw (had to google, now I want some) but probably nobody would care.
Wealth and a cultural aversion to the trappings of poverty. Rich people don't need to eat offal. My dad hates the taste of liver because he associates it with the cheap liver and onions he choked down as a kid. Same with tongue.
That's definitely a lot/most of it, particularly with offal, but plenty of countries have gone from poor to rich and kept eating blood sausages and sweet breads and it doesn't explain like why lamb or goat is a specialty meat. Rabbit exists in a weird liminal not quite game not quite specialty.