To ask about people from different countries

I think about this sort of thing a lot. Much of it is down to socialisation. So if you grow up with excitable people who have large outdoor gatherings you're more likely to develop that behaviour yourself. There will be outliers, of course, who might feel they don't fit in, because they don't like large groups or noise, for example.
Similarly, if you lived in Austria in the 18th century, you weren't necessarily born brilliant at music. But you were exposed to beautiful music from a young age and developed an appreciation early and became part of that huge audience that encouraged the great composers.
Liverpudlians are renowned for their quick humour. They can't all be naturally funny though (well, it feels unlikely). But they learnt how to quip and parry at their mother's knee and gradually became experts.
It all fascinates me... Great post, OP!

We went to a family run Italian restaurant in Newcastle, many years ago, our ds was about 6.
The clientele were mostly families and I’ve never forgotten the happy chatter, the well behaved dc and the feeling of warmth.
I've never experienced such a happy restaurant since.

Amusingly dh and I were in Switzerland and went to eat in an Italian restaurant. Turned out the owner was Greek. He insisted that we sit on the terrace so that he could talk to all of his clients and get us to talk to each other. By the end of the evening we were all chattering across the tables and the Greek owner was mortified that he had no Baklava when I asked if he did Greek desserts.

My dil is from S. Wales, different again to N. Wales. Dgs was born and is being raised in N. Wales and as a pre teen is very proud that he is welsh.

I think Northern hemisphere citizens tend to be outwardly polite but not as openly chatty as southern Europeans.
However I’m sure many people will have different experiences.

Not sure you can attribute it to specific countries. On a recent trip to Spain, I found the locals in Seville to be surly (towards tourists anyway) whereas the locals in Malaga city centre were friendly and welcoming (in spite of recent publicity saying they want tourists to "go home".

What makes a culture? So much! Weather, social, economic and political history, the influence of literature and the arts…

Yes you could probably change British to Welsh/English/Scottish in the OP, and that is sort of the OP's point. I'm Welsh and there's even a difference in culture within the home nations. The OP is just asking why that might be.

I think the culture in which you grow up has a huge impact, even within countries, north vs south England there can be significant differences.

What do you mean by 'English'?

I'm from Wiltshire......... 🤣

I wonder this myself often. I grew up in Spain, and the Spanish are so different to the British, right from childhood. I think it is to do with the weather, socialising habits including meal times, and surrounding environment.

But what do you mean by British? I’m Welsh but culturally different to English, Scottish and Northern Irish. I think you’re looking for stereotypes.