Two decades after the attacks on Sept 11, 2001, the United States continues to grapple with the aftermath of that day.

Former officials, historians, pundits and those who have lost loved ones in the tragedy reflect on the lessons learned from that day.

On the East Front steps of the Capitol 20 years ago, about 150 members of Congress－both Democrats and Republicans－gathered together in the evening with many holding US flags in their hands and in the pockets of their suit jackets. After observing a moment of silence over the tragedies of the day, those assembled broke into an impromptu rendition of God Bless America.

"We were setting aside all of our differences," said California's Representative Adam Schiff, who was on the steps and only nine months into his first term as a congressman at the time. "We were all expressing our love of country and our commitment to protecting it, and a resilience in the face of this attack."

Now, the 61-year-old said Congress is a very different place from 20 years ago. "It's a far more partisan place… There are more members there to tear it down than there used to be," he told the Los Angeles Times.

In an article titled The World 9/11 Made for the Project Syndicate website, Richard Haass, president of the Council on Foreign Relations, wrote that it is necessary to ask what difference 9/11 made beyond the immediate costs, as neither the US nor any of its allies has experienced another attack on the scale of 9/11－or one even close to it.

"How did history change, if at all, as a result? … Today's US is more divided than ever at home and increasingly disinclined to carry out the sort of active foreign policy that has been its hallmark since World War II's end, and which has, on balance, greatly benefited Americans and many others," Haass wrote.

"In hindsight, we can now see that 9/11 was a harbinger of what was to come: less the globalization of terrorism than the terrors of globalization. The attacks conveyed the message that distance and borders count for little in a global age. Little stays local for long, whether terrorists born in the Middle East and trained in Afghanistan, or the effects of the global financial crisis that had its origins in American financial mismanagement."

In Shanksville, Pennsylvania, where four al-Qaida terrorists drove United Airlines Flight 93 into a field after a heroic revolt by 40 passengers and crew members, 87-year-old Sylvia Baker said there has been separation and more distance in the years following the tragedy.

"The people that were here and felt the shock and were involved the first year or two, they don't mind talking about it," she said. "But the people who came in or grew up since then, who weren't as affected by it? It's not a topic of conversation."