9/11 _enabled_ the Bush admin to provoke a war on an unrelated country, which destabilized even further an already complex area.

It's not like it was an automatic consequence. It was a choice.

If we're discussing events significant enough to be considered in a historical context as having changed things enough to warrant the claim that "the 20th century ended then" then no, 9/11 is not fundamentally significant in my view.

Soldiers sent to war and suffering happen. In itself it is not historically significant, neither is an invasion in itself. You could argue that the Soviet invasion of Afghanistan was more significant because it fueled islamist extremism and the US backing of Al Qeada... While the US's invasion of Iraq has its root in the 80s and 90s, with 9/11 being only a convenient pretext, and does not seem to be hugely significant historically.

Everything changed when the Berlin Wall fell/the Soviet Union collapsed. The reality is that nothing really changed on 9/11. An emotional perspective is not a historical perspective.

9/11 was significant because of things done in the name of it: endless wars, growth in the surveillance state, militarization of police. Those seem fundamental, and it all happened as a result of 9/11.

None of what you mention really started with 9/11 or is really significant in a global historical context, and especially if you want to debate when the 20th century ended, which ought to be based on global, key changes.

Edit: Arguing that the 21st century started with 9/11 seems both superficial and American-centric to me, like your reply to this comment below. It misses the big picture, the global context.

The PATRIOT Act was justified with the intelligence failures that led to 9/11. The militarized police get much of their gear from surpluses sold off from the endless wars justified by people no one would challenge because of "with us or against us" rhetoric following 9/11. Their funding comes from bills justified with "terrorism!" cries from people who feared a stranger with a bomb more than a cop with an armored personnel carrier following 9/11.

Yep. 9/11 was what started the return of Fascism and the fall of Western Democracy.