It is hard to imagine those zealots engaging in bombings in New Jersey or in Bavaria, although they constitute a serious threat to their coreligionists in their own country (they love to attack the Shiites). The majority of them do not master any foreign language and could never get a passport..
This is a serious and complex country like Iraq or Pakistan, but not much in the world.
It goes without saying that nothing can justify these deaths, but it is still wedded to state suspect that something that kills an average of 1500 non-Muslims every year on a planet that has nearly seven billion people is the greatest threat today.
During the Cold War, the United States and the Soviet Union had 10,000 nuclear warheads ready to be launched against the enemy. If war had actually broken out, hundreds of millions of people died, or even several billion if nuclear winter. Besides the two countries had also biological and chemical weapons quite terrifying.
If radical Islamists were able to obtain nuclear weapons, it was a single bomb, not 10,000. Assuming they manage to make it explode, it would cause a disaster at the local level, but not a global holocaust. The gas attack on the most serious so far in 1995 in the Tokyo subway, has only 13 victims, and although biological weapons are potentially very deadly, they born quire highly specialized scientific expertise.