An international team of counter-terrorists is a great idea, but likely to remain a fiction. Tom Clancy is noted for the realistic plots and details he presents, but there are many obstacles to this kind of international cooperation. My reasons for thinking this would be difficult, if not impossible, to accomplish are somewhat cynical, and someone else might have a more optimistic take on this question.
It has always been difficult to achieve international cooperation to accomplish anything, but in recent years, in my opinion, the United States has squandered its credibility in many ways, first by Bush's worldview of good and evil, with no shades in-between, and with a war begun on a premise that proved to be a lie. You may have noticed that very few countries are any longer interested in committing their resources to causes that the United States advocates for.
Another reason I think such a force would be difficult is that the attitude of the United States is generally that we must be in charge of everything. If such a counter-terrorism group were begun, we would want to take charge of it. But in today's world, where the United States is not necessarily the leader economically, politically, or morally, there are not many nations that would endure this attitude. Consequently, there would be problems with such a group.
Another issue that arises is that the United States in recent years has acquired a reputation for sanctioning behavior that most civilized countries consider to be torture. There is evidence to suggest that we have violated international law in our torture methods. What rules would an international group of counter-terrorists play by?
There are some entities that are, on paper at least, examples of international cooperation, the United Nations, for example, Interpol, and the international tribunal, the World Court at the Hague. But each of these institutions has problems, for the above-stated reasons and many more.
It would certainly be wonderful to have such a group. If we can learn to follow the rules that people are supposed to learn in kindergarten and learn to cooperate and play fair, perhaps terrorism can be conquered!