1. IME a lot of the Welsh have been quite horrified at what it has cost. Many arguments could arise re (for example) free prescription medicines for all.
2. 16/17 year olds - this is a big problem IMO. It is absolutely verboten for a teacher etc. to have sex with a pupil under 18 (criminal offence). It is also an offence to have an 'indecent image' of an under-18 yo. So if a soldier (for example) is legally married to a 17 yo wife and she texts him a picture of her tits to keep him company on the battlefield, he is a sex offender ('paedophile') and maybe so is she. The law is clear, and it is a sad state of affairs if authorities have to wriggle about. By the same token, a 16 yo can vote but NOT be trusted to buy cigarettes (verboten) or beer in a pub (ditto). Are 16/17 yos children or adults?
3. Ah, regions within countries. How far back should we go? The Cornish have affinity to the Welsh and the Bretons. France and Spain are relatively recent modern 'countries'. As I understand it, the 'Scots' were never really a unified people any more than the Welsh are nowadays.
4. On the same point, is the US now really unified? History would suggest not - the US was formed comparively recently by colonial conquest, purchase, intrigue, etc.
I must confess that I have a wry smile when ANY country seeks to stress its unique heritage. The more we learn about history and pre-history and the movement of peoples, the more we realise that we are all the product of immigration, inter-breeding, and so on.
Just as a recent example - in Wales, some people are hung up on the Welsh 'mining heritage'. They overlook the fact that many immigrants came to Wales for jobs in mining, etc. My own family were, I think, Hugueonauts from Europe but my paternal family were robust, Welsh-speaking, colliers.
The latest news shows not only the presence of Neanderthal in our genes but also the DNA of groups who migrated from Siberia, Africa, Southern Europe, etc. IMHO it's time that the world's people came to recognise that we are all homo sapiens and we'd better start to get on with each other. But that's just me.