The USA is older than the Republic of France. Why then is France still considered to be an older nation? Is it because the idea of a French state is older? Is it because people have identified as French longer than American? How would long established American Indian groups affect this idea? I am not trying to diminish the age and history of old European countries, I am just interested if there is any contention out there or a standard to measure a nation's age.
France as a political entity has existed since the establishment of the Kingdom of France in 843AD. From that time until the present day the nation of France has undergone many changes of government and bureaucratic structure, but those changes in government form do not mean that 'France' ever ceased to exist as a political entity/nation. In a sentence, changes in government are not the same as is changing the nation. The Republic of France and the Kingdom of France were the same nation with different governments.
There is no yard stick by which a nation can be measured. A number of factors must be taken into account. One of them is political self-governance which is why the USA is often considered to have been born after the Revolutionary War.