The text states that defending the US against terrorism is difficult. Why was especially difficult to defend against a threat like Osama bin Laden?

the wake of the terrorist attacks of September 11, 2001, the United States launched an international war on terrorism defined by military intervention, nation building, and efforts to reshape the politics of the Middle East. As of 2017, however, it has become clear that the American strategy has destabilized the Middle East while doing little to protect the United States from terrorism.

After 15 years of considerable strategic consistency during the presidencies of George Bush and Barack Obama, Donald Trump now takes the reins having promised to “bomb the sh—” out of ISIS and “defeat them fast.” At the same time, however, Trump broke sharply in his campaign rhetoric from Republican orthodoxy on Iraq and Afghanistan. Whatever President Trump decides to do, an evaluation of the War on Terror should inform his policies.

We argue that the War on Terror failed. This failure has two fundamental—and related—sources. The first is the inflated assessment of the terror threat facing the United States, which led to an expansive counterterrorism campaign that did not protect Americans from terrorist attacks. The second source of failure is the adoption of an aggressive strategy of military intervention.

The lessons from the War on Terror indicate that it is time for the United States to take a different approach. Policymakers need to acknowledge that although terrorism is a serious concern, it represents only a modest security threat to the American homeland. Further, the United States should abandon the use of military intervention and nation building in the War on Terror. Instead, the United States should push regional partners to confront terrorist groups abroad, while the U.S. returns to an emphasis on the intelligence and law enforcement paradigm for combating the threat against the American homeland.

b) the confederacy had to pay all union war expenses.