The evidence indicates that the events of September 11, 2001, ultimately made the United States stronger by creating a renewed sense of national resolve and unity to fight terrorism and defend American values. The attacks ended the notion of American invulnerability and isolationism, pushing the country towards a more engaged and focused foreign policy and defense posture. The passage states that September 11 was comparable to Pearl Harbor in shifting American attitudes from isolation to active global involvement. It led to increased defense budgets, greater emphasis on international cooperation (multilateralism), and a determination to combat terrorism worldwide. The attacks unified the American public behind efforts to maintain democracy and liberty both at home and abroad. The result was not withdrawal from the world but reinvigorated engagement with key allies and a commitment to confronting terrorism and its root causes.
Thus, September 11 strengthened the US by transforming its foreign policy, defense priorities, and public resolve to confront new global threats effectively.