In 2001, the United States invaded Afghanistan in response to ?

"We did not ask for this mission, but we will fulfil it," US President George W Bush said when he announced the first air strikes against Afghanistan on 7 October, 2001. The raids were in response to the 9/11 attacks, which killed 2,977 people in New York, Washington and Pennsylvania.

a big wall across the mexican border so no drugs, terrorist, or illegal immigrants can come through : )    

the us constitution is a living document, meaning that it can be changed over time as the country changes.