Terrorism is a tool for people that have very limited resources and power to act. And yet, with just a very little, they are able to make a big noise. What can a fly do to a bull? A fly can't fight the bull, it will simply be seen as a distraction or annoyance. However, if the fly can get into an ear of the bull, the bull will eventually go mad and destroy everything around. This is how terrorism works.
There really has not been many people killed since 9/11 because of terrorists in Europe or America. Usually attacks result with casualties of around 50 to 100 people. 9/11 set a new record with a death toll of nearly 3,000. But that is still a very small number compared to battles during wars. For example, during the Battle of the Aisne, there were 250,000 people killed (First World War). And each year deaths due to accidents are much higher (i.e. 40,000 people in America or 80,000 in Europe). This is much more than that caused by terrorism. Yet we hear a lot about terrorist attacks. This is because of the media, which is a great tool for terrorism to spread its fear and political disagreements.
We live in the safest world that humanity has ever had.