I understand some resources like fishing resources could only available to coastal countries and I think that's a good idea,
but in regards to ground resources there has historically been a lot of mines of all different resources like coal that have been located beside coastal areas. A lot of people have no idea how a wide array of resources can be found in one small area. In my state alone for example in the 19th century there were hundreds of gold mines and probably thousands of coal mines, and I don't know the specifics but I'm sure there were various other resources being mined, many of these mines were located beside the ocean, rivers and bays, and now there are none today, but back in the day they probably hadn't even scratched the surface of available resources in the ground. The average person has no idea how many of all sorts of resources are right in their back yard. A lot of people are perhaps unaware the world is a big pile of various resources. Although its true that not all ground resources are available everywhere, they seem to be in a lot more places than not, although they're just not being extracted is what I'm saying. People all over the place are living right on extensive veins of resources and they have no idea.
Now if Simcounty had climates than highly desert (sand dune) areas should have very low or no wood resource availability for example, because they don't have much more than the occasional palm tree to cut down. In regards to agriculture, deserts can be irrigated however so perhaps they will have a higher startup cost or overhead. As well perhaps highly arctic (very cold) areas would have similar increased overhead for agriculture as desert areas, because they would be more dependent on greenhouses and electric heating. and I'm sure theres other examples, like if offshore oil was a resource than it'd only be available to coastal areas. Offshore oil could be similar to a standard oil operation, but have a different set of overhead than ground drilling. I'm not sure but overhead on offshore sounds to me more expensive, building maintaining and supplying a mechanical island, so I'm not sure the advantage there. A shot in the dark here but perhaps the offshore drilling method allows for greater output rate of oil.
I wouldn't go so far as to restrict iron ore, minerals and other highly abundant resources to only certain regions though. Iron is one of the most common elements in the world. The world is literally comprised of abundant resources such as iron. I don't really know much about minerals, but as far as I know they're all over the place. There's minerals literally in my backyard, that are so abundant they're worthless. because every land had been underwater at some period in time, as well receive rain on some level of consistency, I think that's contributed to minerals being every where.
The larger reason why certain resources are extracted in certain regions is probably moreso currency exchange rates, regulations, taxes and cost of labor, than that these abundant resources are just not available in certain terrains and elevations . . . I think that is more accurate in regards to agricultural resources like fish, wood, bananas, coffee, etc, but until Simcountry has a climate system I can only think of fish as a good example right now of a resource that should be restricted to certain areas. . .