While it is impossible to know the figures. The majority of Americans have had some exposure to the items on your list. I’m guessing that if you haven’t tasted at least some of the meals mentioned by adulthood, it’s because you didn’t want to, rather than because you couldn’t get them. Crab, lobster, oysters, and some caviar are all reasonably easy to come by in the United States. Foie gras is a less popular cuisine, and many people consider its manufacturing to be cruel. This makes it more difficult to sample than its cost. Beluga caviar is expensive and difficult to come by, so it’s unlikely to show up on a typical seafood buffet menu.
I don’t have exact data, but based on my own experience, it’s definitely a lot more than you’d think, potentially as much as a third or more. Not that Americans can’t afford it; I’m sure plenty of them can and do indulge in high-end meals.
The reason, I believe, is that I get the perception that most Americans prefer a fairly “limited” choice of meals. My son-in-law, for example, avoids clams, oysters, and mussels. He refuses to eat duck or lamb. Mushrooms and melons are also off limits.
When I brought a close buddy, a VP in Silicon Valley, out for lunch in Las Vegas and ordered grilled duck, he informed me he’d never had duck before. Even though he’s a retired butcher, my next-door neighbor refuses to eat lamb or duck.
Most Americans (please excuse me if I’m wrong, all my American friends and relatives) are meat-and-potatoes eaters who seldom go into “strange” meals.