Well, we discovered that we needed to upgrade security so that potential criminals weren't coming into our country, and so potentially harmful substances weren't being brought onto our planes. That meant literally anything that could become a bomb, start a fire, stab someone etc. As for Pearl Harbour, I think that had more of an affect on how we thought our military and defence system was working.
Answer:
Yes
Explanation: because some countries sell a lot of their things to be able to pay for the wepons that the military needs. And alot of things gets destroyed because of war going on.
Under the Truman Doctrine, the United States became committed to helping countries that were a) fighting a Communist takeover.