My mother used to like frogs legs and if she saw them on a restaurant menu, she would order them. I tasted them once and to me they just tasted like watery chicken. Not awful, but nothing I'd go out of my way for. I haven't seen them on a restaurant menu in years.
I used to see things like beef hearts and tongue in our regular supermarkets, but things like that have disappeared from the generic type stores. However, many ethnic markets have started popping up around town. Big ones too, not little mom and pop places, but big chains. A Mexican market just opened up quite close to me, having moved into a closed Albertsons, called Cardenas and I've seen offal there. It's a very nice store and their prices are very reasonable. They don't have the best grade of beef, though, very little marbling.
I've seen some strange (to me) meat items for sale at the International Marketplace. Things like pig uteruses and beef tendons. I once saw a man loading several packages of beef tendons into his cart and I wanted to run up to him and ask him how he cooks them. I didn't, though. Too shy. Heaven knows what one does with a pig uterus. The IM does carry some British sausages in their frozen department and some British biscuits as well. It's all rather pricey due to the rate of exchange.
I don't eat offal, however. The closest I've come was with liver and I hated it. My mother liked it and cooked it for dinner on occasion. When I was a kid, I'd come into the house for dinner and smell the liver and onions and burst into tears. Since I left may parents' house, liver has never passed these lips. My husband likes it but I've told him if he wants some he can cook it himself. I can't stand the feel of it raw whilst taking it out of the package.