http://penelope.uchicago.edu/Thayer/E/Roman/Texts/Polybius/6...
Of course, he stopped writing towards the end of the second century BC when Rome’s Republic began to slowly fall apart, but even the Empire that came after proved somewhat durable.
People consider Norway or Switzerland durable because they lasted 800+ years so far.
The Eastern Roman Empire, as a continuation of the unified Empire, lasted more than twice as long, on much bigger territory which attracted all sorts of external invaders (Goths, Persians, Arabs, Slavs, Crusaders, Venetians, Turks).
Compared to the ancient-ness of the Romans, England and Sweden are middle-age countries, the US is a youngster with a fresh driving licence and the EU is a toddler who can barely say "mama".
Of the currently existing countries, only Japan seems somewhat comparable to the Roman Empire as far as continuity goes, and it is an island state well shielded against invaders by the sea and its fierce storms.
In reality, Denmark is one of the only countries in (Northern) Europe to have been completely independent for a milenia .
France has lasted longer than that so far, more or less since Clovis I was crowned king of the Franks in 509. (it does not disprove your point, that's just for context).
> the EU is a toddler
The EU is not a nation or a state, and does not pretend or try to be one; it's a strange thing to include in your list.
On the other hand, mere Christianization of the Roman Empire doesn't seem as crucial (pun intended) as to create a break in its statehood. Most of the institutions went on just like before, most of the important families stayed the same, the legal system and the language of the realm didn't change at all or only very little etc.
The republic period is more interesting, but I believe that the Romans considered themselves the same people and the some country in that period, without breaks in identity - which IMHO should matter more than a purely academic take from the early 21st century.
From where I live, the disintegration of the Austro-Hungarian empire put a lot of economical and ethnic strain on the successor states, destabilizing the entire Central European region and making it an easy target for imperial intents of Germany and Soviet Russia.
And even today, in Czechia of 2022, we have a lot of A-H legacies in our daily lives, like paying with "the crown" and using the same kilometre markings along our railway routes, beginning with 0 = Vienna.
Empires tend to consist of much more than just the ruling class.
I don't think the EU should be in that list at all, as it isn't a nation. Not by the UN definition, nor by its own.