I was on the west coast in an airport when this came down. Long story that's not different from a lot of others but I ended up driving across the country from California to South Carolina. I listened to a lot of talk radio and to a lot of news. I stopped each night and chatted with people in hotels and restaurants. Fear was rampant. While I didn't observe anyone running around like their hair was on fire, there was a great deal of anxiety and unease immediately after the attack. The entire air travel system shut down, guards on chemical plants and nuclear plants, etc. that good old all-American practice of price gouging worked on Mr and Mrs America because of fear. Anyone who lived in the U.S on 9/11 and wasn't afraid for their family members, friends, co-workers, or themselves is in a very small minority.
Fear isn't a bad thing. Panic is bad, fear can keep you alive. I've been shot, I've been blown up, I've ambushed and been ambushed. Fear has worked very well for me.