I can only imagine that banning something would only increase the demand for it, though haggis may be the exception that makes the rule. In any event, it is certainly available, only it will take some looking to find it. If anything, over the years, more and more different kinds of foods have become commonly available (Haggis still being an exception) to cater to immigrant populations. That's undoubtedly true in the U.K., too. Incredibly enough, pork products are available in the Middle East, though demand isn't high.
Two things probably would have had an impact on cooking and eating habits since the Civil War, which was at the beginning of the day of the open range cowboy. The first might have been refrigeration. Those living on farms may have had a springhouse or even an ice house but those living in very temporary camps next to the chuck wagon would not have even had that, and still wouldn't, if they still camp beside a chuck wagon. Generally speaking, there have been a lot of changes in food preservation and storage, although some, like canning (and salting and drying) had already been in use by then.
The other thing, at least as far as home consumption, is convenience foods. Traditionally, everything was prepared fresh at home, after a fashion. It may not have been all that fresh in three or four days but it was all prepared at home. In Europe, I understand that buying bakery-baked bread has been the custom for ages and that home-baked bread was not common, though I suppose that varied by region, too. These days, many main dishes can be had in a heat-and-serve basis, like frozen pizza. Home canning supplies (glass jars and lids) are available where I live, though I don't know who still does that. It only makes sense if you have a large vegetable garden. Also, foods that were once available only seasonally, like tomatoes, can be had year-round, and some fruits, like oranges, were essentially imported foods in some parts of the country and relatively expensive. You might get one at Christmas. Nowadays, cut flowers are even available at the grocery store all year long. In the winter, they are flown in from South America. It's hard to believe.
Shortbread, genuine Scottish produced, is available here, as a speciality dessert type item but all sorts of European dessert type candies, cookies, chocolates, and confections are available here, some wide available, others available in specialty shops.