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I can't help notice how decline of democracy is painted as the 'end of the West', meanwhile Medieval Era was the 'spring of the West'. There is no democracy in Medieval West, there were kings, theocracies, crusades, burning of heretics and women.That's because what's important is the vector, not the absolute state. Towards the end of the medieval era we saw the emergence of all kinds of positive developments, plus increased prosperity, order, etc. And of course it was followed by the Renaissance.
Similarly, now we see all kinds of degeneration, including the most major: the western countries fall down several steps in the top 10 of GDP, giving their place to Asian countries. The West increasingly loses importance economy wise, and this also means declining standard of living, infrastructure, forward momentum, political discontent (Trump is an example of that), and cultural relevance. It's a slow process, which will take decades or even a century to be completed, but it will be completed.
>So here comes the real question: What is the west?
Historically/Geographically, the Europeans and their ilk in the USA/Canada.
Culturally, the mix of Roman law / Christianity etc as it progressed through to the Renaissance, Enlightenment and on to the 20th century.
Economically, sometimes "westernized" places like Japan and South Korea are included (and Australia/NZ).
In any case, it's mostly: what's not culturally Asian, African, Latin American, or Arabic.
> Culturally, the west now is way more different then the west in 1500 as versus the East today.
Yes, but that's neither here nor there. Physiologically, mentally, etc. a 60 year old is more similar to another 60 year old than to his 5 year old self. But despite that the 60 year old and the 5 year old are the same person - and share their development history.
>Why is it that people start feeling that the west will pass - and that it somehow coincide with demographic changes
Because that's how it happened for other similar cultures/countries in the past. Including for a succession within the west: In the 20th century Britain as an "empire" declined and gave way to the USA, for example.
Also because it has already began giving its place to developing economies that have began to surpass it, and have more momentum.
>US have been through much worse, from the America First nazi sympathizer of the 30s to McCarthyism of the 50s, that's not even mentioning the civil war of the century before that
Those are not "much worse". Those are historical developments in a country with a positive momentum vector and huge development (economic, population, global relevance, etc) during and afterwards.
>We as humans tend to characterize what we're currently moving through as more significant than they are - put it into historical perspective and it could just be a 'nah'
In history few powers (or superpowers) remain in their place for long.