One of the things that has fatally weakened western civilisation has been the Culture of Mockery. This has been particularly the case in Britain.
Take a look at British popular culture over the past half century. It's nothing but a sustained campaign of mockery of traditional Britain. Back in the 60s we thought this was being done by the counter-culture - by bold avant-garde nonconformists attacking the Establishment. But it wasn't. It was the Establishment doing the mocking. Tearing down everything that ordinary Britons cared about.
The British people still haven't figured out that it's their own Establishment that hates them. The political, cultural, financial, bureaucratic Establishment. The hilariously misnamed Conservative Party. Even the Church of England, which has nothing but contempt for actual Christianity. Even the Monarchy, which has stood by and cheerfully watched while the country was trashed, occasionally rewarding the worst traitors with a knighthood or a peerage.
It's not the global left that has destroyed Britain - it's the British Establishment.
Never underestimate the absolute loathing that people like Theresa May have for everything Britain once stood for.
Of course the Culture of Mockery has undermined all western societies, but it has assumed a particularly virulent form in Britain. The British elite has waged a continuous and all too successful war on Britishness.