I might be wrong, but it seems to me that two categories of countries exist in Europe.
Old countries, that existed for a thousand years or more (France, Sweden, England).
Young countries, Germany, Italy, Croatia etc... that were formed after reunifications or divisions (so I guess Austria is in the list since the "imperial" Austria and "modern" Austria don't have a lot in common when it comes to territories).
My questions are the following. Why only these three countries (more?) managed to survive that long without ever being split in many small pieces like the HRE or Italy and why no other country in Europe seemed to be able to do that? And why didn't the "big" countries took this opportunity to invade the small and divided one when they were the weakest?
Thanks in advance for the answers
I think you might be making some unnatural delineations. England wasn't a distinct 'country' over the last thousand years, considering it was ruled by the Norman French for quite some time. And those Norman French were not the 'Parisian' French you're thinking of, who were the Capetians, who conquer Normandy in the 1200s - much of France was not controlled by the Capetians when they came to power, and they had to conquer it.
By comparison, Kiev has been a center of power in Eastern Europe since well before Moscow was, but it has been passed around between other rulers in conflicts in that region. I would hazard that many of the 'young' Eastern European countries just never had steady centers of power. Except for a brief invasion or two, Moscow has remained very important and powerful over a long time period. Prague was the seat of the HRE for some time but after that didn't really recover its significance. During Italy's turbulent recent past Rome, nor anywhere else, was a particularly stable center that could claim legitimacy over the whole country. I think whether or not Germany can be said to be the successor of the HRE is tied up in its relationship with Prussia and the Westphalian treaty, and would be an interesting topic for a paper.
Of course, this is all about perception. These lands have all been consistently settled over the last thousand years, the only difference is who ruled them.
I see a problem with definition here.
If Austria today can't be seen as continuous with Imperial Austria, can France today be seen as continuous with Imperial France? What about all the colonies it lost? The territory it lost during the Napoleonic wars?
The same could be asked of England, Portugal, Spain, the Netherlands, and Sweden
Also, these countries had different levels of internal cohesion at different times. When does France become 'France' as opposed to a bunch of Franks, Normans and Occitan dukes who are vassals to a crown?
Edit: Each country will have a unique history. One thing you could as is "who is the last person to conquer and hold this area?" The Nation-state has always been a bit of an aritifcial construction. It's very difficult to actually define.
The idea of nations itself isn't as old as you might think.
