Geopolitical changes are deffinitely possible. Natural landmass shift would take very, very long time to be really noticeable though.Let's say our story is set in the very distant future, right? In theory, could different climate, geological, and political changes influence the appearance of a new country? Surely, it'll be based on some countries and probably take after them, but it'll still be different and independent, have its own government system and everything?
I've watched a few videos and looked at a few maps that describe earth continents if all ice melted, and the very possible future of the continents due to the geological changes, meaning how the landmasses would move and therefore change the modern look of Earth. And I thought... Could it be possible for a new country to appear in the very distant steampunk dystopian future, the country that I could use to set the story in, so it'll be more confortable to operate with. Like... Like Gotham, the city that exists near real cities, but not for real?
Supervolacnoes and powerful weapons could also change landscape to a limited extent (possibly with resulting volcanic/nuclear winter), and if we're talking about distant future, large-scale landscaping could have an effect as well.
The wars, civil wars and disasters would certainly see some governmets rise and fall. Power vacuum would allow new nations to form, maybe nomads would emerge as well, if they could secure all necessities on their travels, by trade, raiding or being fully self-sufficient. Major corporations carving out some land for themselves is also possible, athough question is how they would transform over time if they survived to the 'present day' of the story.