It's not like it was an automatic consequence. It was a choice.
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.
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.
9/11 was a spectacular event but did not change anything fundamental and was neither the first nor the last Islamic terrorist attack in the West or on the West/US. In fact, the lid had been removed on Islamic extremism in the 90s, following the collapse of the Soviet Union, even if it had been brewing for quite some time before that: Soviet withdrew from Afghanistan in 1989 (leading to the Talibans seizing power), Algerian Civil War started in 1991, highjacking of Air France flight by Algerian terrorists in 1994 (said to be the blueprint for 9/11), attack on US Embassy in Nairobi in 1998, attack on USS Cole in 2000, etc. I think what 9/11 did is to make the American public catch up with the world they were living in because many of them had not realised yet.
I'm not sure whether Covid-19 will change anything in the long term. It's too early to say. At the moment the main effect seems to be a significant economic downturn, which could have long term consequences, or not.