Upsetting these arrangements is a major thing for the nations who have been free of terrorist activity for many years. The stable democracies of Western Europe can handle a crack down on terrorists, and terrorist supporters, living in their countries. Not so for Moslem nations like those in the Middle East and South Asia (Pakistan, Bangladesh.) Saudi Arabia, Yemen and Pakistan are particularly vulnerable. In these countries, Islamic radicals are a major factor in local politics. A campaign to round up terrorists and their supporters could lead to major unrest, perhaps even civil war. A radical Islamic government in Saudi Arabia would probably still want to sell its oil, but more of that money would go to supporting Islamic radical movements and terrorism. Even now, many wealthy Saudis contribute to Bin Laden and other Islamic radical groups. Many do it because they believe in the cause, others do it to buy some good will in case the radicals take over. Same situation in the other Persian Gulf Arab nations, although none of them have to deal with the same intensity of feelings in Saudi Arabia. That nation is the home of the most sacred sites in Islam, and the locals feel a more intense dedication to Islamic radicalism.
But there is some real enthusiasm among most nations to finally get together and crack down on terrorism. The problem here is that, for many countries, their local terrorists are seen by some other nations as freedom fighters. Russia considers (with some justification) their Chechen rebels as terrorists. They Chechens have committed some terrorist acts in Russia and they are connected with the Bin Laden organization. Chechen's have been training in Bin Laden's Afghanistan camps. China considers is Islamic Uigher separatists to be terrorists and it has claimed to have broken up one Islamic radical group (the East Turkestan Party of God in Xinjiang). Buddhist Tibetian separatists are also classified as terrorists. Many nations condemn Russia and China for their crackdowns on local terrorists, and there will have to be a change in attitude to obtain any cooperation from those two nations.
Each nation containing terrorists will require the attention of more diplomats than soldiers. This is basically a diplomatic war, backed up by military forces. Yes, we can send in the B-52s (from Diego Garcia) to carpet bomb the camps in Afghanistan. We can invade Iraq and replace Saddam with someone else (who may be worse), but in the meantime the Iraqi terrorism support disappears. We can bomb the Hizbollah camps in Lebanon, although many of those are surrounded by civilians or dispersed into caves and bunkers. But the terrorists have to be arrested, and the people best able to do this are local police. This is a war where allies are not just useful, but absolutely necessary. So for the second time in 12 years, Colin Powell gets to lead a major war effort, this time as the Secretary of State.
Limits- Although every nation in the world, except Iraq, has signed on for America's war on terrorism. But many of these nations have already found ways to deal with terrorism. The most common solution has been to make informal and unofficial truces with the terrorist groups. In Europe, this has been common over the last few decades. Normally, Americans hear nothing about these arrangements, until a captured terrorist is not prosecuted, or released early from prison. Italy got caught doing this, as did Greece. But France also let it be known, discreetly, that terrorist groups could operate in France as long as they didn't do anything in France. Such arrangements are common is Moslem nations. Where these deals don't usually apply is where the terrorists are local, not international. But even here, there are arrangements. The 25 year bombing and shooting campaign by the IRA in Britain was constrained by an unofficial policy of assassinating IRA men when the organization went over the line. The rules developed over the years. When the Earl of Montbatten was killed, the SAS was allowed to kill some IRA men who were not in prison or otherwise officially under investigation. The deaths of these men could be attributed to internal disputes or pro-British terrorists. Over the years the list of no-no's came to include; no royals, no foreign adventures (there were IRA attacks in Germany and Gibraltar), no animals (some horses were killed during an attack on the Household Cavalry, the British have a thing about harming animals), the use of certain weapons like .50 caliber sniper rifles and a few other no one but the IRA and SAS are sure about. Of course, no one can prove this policy exists, but those who follow IRA activities, and the IRA themselves, have no doubts.