After the attacks on September 11, 2001, how did U. S. foreign policy change?

Probably the most noticeable thing that happened after the 9/11 attacks were the amount of intervention we had with enemy countries that posed a threat to the US. During this time the word "terrorism" was first really established to explain the acts of the enemy. There was also a lot of defensive spending to protect the homefront to prevent another 9/11 from happening.