What is a good response to this
I think the future of terrorism is that it will continue to expand (slowly) within extremist elements of the Islamic community in the United States but it will be contained.
Fortunately, we have two oceans as natural barriers from unvetted migration from countries that are hotbeds of Islamic extremism.
Our northern and southern neighbors are also relatively free from terrorist activities. The outlook on terrorism however, is much bleaker in other parts of the developed western world.
Progressive liberal European societies are not equipped to deal with terrorism. They believe (mistakenly) that they can negotiate with extremist elements which are taking hold in their countries.
This soft approach to terrorism will leave them exposed and victimized in greater numbers every year until they take a harsher stance or cease to be the dominant authority in their own countries.