The US went to "war on terror" after September 11, 2001 terror attacks orchestrated by Al Qaeda that left 3,000 dead, the worst-ever attack on America post Second World War.
Stephen Collinson, writing in CNN said September 11, 2001, doesn't explain everything. But the war on terror took America in a political direction from which there was no coming back as after those twenty years on, it is at war with itself, its democracy threatened from within.
In hindsight, the attacks heralded the dawn of an era of political trauma and turbulence that snuffed out a brief period when the prosperous US had basked in a post-Cold War glow of peace, standing as a lone superpower.
In retrospect, it's now clear that despite the heroism of thousands of troops killed or maimed in post-9/11 wars, the excesses of the US political response caused as much, if not more, upheaval as the attacks themselves.
A sharp, successful war in Afghanistan bogged down into a 20-year quagmire that ended only last month. Another war in Iraq, fought on false pretences, was its own early version of a Big Lie, says Collinson.
President George W Bush went from being a champion on the rubble at Ground Zero to a leader destroyed by his own war.
His successor, Barack Obama, spent two terms struggling to bring the anti-terror campaign within the law and international morality, but his use of lethal drone strikes to take out terror targets also caused civilian casualties and was condemned by human rights advocates, says Collinson.
And along came Donald Trump, vowing to ban Muslims from entering the US and boasting he was smarter than all the leaders who led years of draining combat.
The political wounds of the post-9/11 years were exposed yet again in recent days, as the chaotic final withdrawal from Kabul brought history full circle: The fundamentalist Taliban -- who welcomed Al Qaeda -- rule Afghanistan again, reported CNN.
Bush once warned of a multigenerational struggle against terrorism. But climate change and the rise of China are now seen as bigger threats, says Collinson.
And the most acute danger from terrorists is now homegrown. Al Qaeda may have failed to hit the Capitol, but the building was attacked by extremists who confirmed government warnings that White supremacy is now the country's top terrorism threat.
After 9/11, America united to defend itself. It failed to do the same when confronted by a president who mounted an assault on democracy (Donald Trump), reported CNN.
Divides also cleaved the country in another national crisis -- the coronavirus pandemic, which kills more people every two days than died on September 11, 2001.
If a new 9/11 happens, it's difficult to believe the national and political unity forged by the first one would be repeated, says Collinson.
Beyond politics, and as he contemplates 9/11 on the 20th anniversary, Tony Brooks -- who served as an Army Ranger in Afghanistan and Iraq -- who now practices chiropractic medicine and authored a book, "Leave No Man Behind," about his wartime service -- laments a loss of national togetherness.
"That was the most unifying event in my lifetime, and since then it felt like every major event that happens in the world just divides us even more," he said.
"It's not the same world, where the mission was greater than self. It was all about us, not me. I think right now it's about me."
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