As a result of 9/11:
The World Trade Center in New York was attacked and destroyed, with many casualties. The Pentagon was also targeted, but the attack failed.
George Bush declared the War On Terror, putting us at war with every country in the Middle East, costing tens of thousands of lives and getting us nowhere (also we're still fighting, though now it's focused on ISIS too).
Airfields more than tripled their security, with the United States becoming one of the most heavily regulated airport places in the world
