I mean, take USA for example, is it even the same country after each amendment? After a Civil War? Civil Rights Movement? Landmark Court Rullings?
One could argue that Modern America began in 1965, with the passing of the Civil Rights Act. Or in 2001 when the Patriot Act was passed. Or in 2009 with Citizens United Court Ruling. Or in January 2017 when… you know. Or in January 2025.
When did the country really start?
Really relies on what you define as a “country”, and how those definitions might have changed across time, or might not even have existed at all.
The US is probably one of the easiest ones.
Enter Europe:
Has the German Reich been a country?
Then what about the Grand Duchy of Luxembourg, which today is undoubtetly a country but has also been a part of the German Reich, following its king?
Similar for other claims of age.
We have e.g. 3 “oldest” cities in my country, each relying on a slightly different definition of “city”.
Even more far fetched: Italian fascism considered itself the continuation of the Roman Empire (the middle ages did not count, somehow). Does it mean that they were 2000 years old for a bit? But then, nowadays Italy consider itself the descendant of fascism (with a tinge of shame) but not of the Roman Empire. Can we pick and choose our lineage?
China consider itself ti have been a consistent country since (handwave) basically forever. Is that enough?
The Reepublic of San Marino has been independent for a very long time, possibly since 301 ce, that would make it a 1700 years old country that never changed its form of government.