The unexpected defeat of the Spanish Popular Party government has been attributed in part to the belief that by joining the US in the war in Iraq, Aznar raised Spain's profile as a target for Al Qa’ida, which now seems most likely to have set the bomb. (This isn't the only way in which the handling of the Madrid atrocity affected the outcome. The government's rush to the judgment, seen as politically more favorable, that ETA was responsible, was criticised by many and contrasted with the refusal of the Socialist leadership to score political points.) The same claim is being debated in Australia.
While there is probably an element of truth in this, it misses the main point. Australia, Britain and other US allies were wrong to participate in the war in Iraq, not because it made us more prominent participants in the war on terrorism but because the Iraq war was irrelevant and in important respects actively harmful, to the struggle against terrorism, represented most prominently by Al Qa’ida.
The irrelevance of the Iraq war to the war on terrorism was evident to most observers even before it started. Even the Bush Administration, while it took every opportunity to insinuate that there were links between Saddam and Al Qa’ida never made a categorical claim to that effect, by contrast with its clear assertions about WMDs.
The pursuit of irrelevant goals at the expense of urgent ones is harmful in itself. The Iraq venture has tied up much of the military resources of the US and its allies, which could have been used to follow through the initial victory over Al Qa’ida in Afghanistan. Instead that country has been left to relapse into “warlordism” and, in some areas, Taliban control. More importantly, the Iraq war dissipated the huge resources of goodwill and credibility that were generated by the September 11 attacks.
But there has also been more active damage. The Iraq war, and the triumphalist and anti-Islamic attitudes of many of its supporters, particularly in the United States, played directly into the hands of the Al Qa’ida propaganda machine, ever eager to claim direct continuity between the Western world and the Crusaders. Combined with the failure to apply any serious pressure on Sharon to settle the Israel-Palestine dispute (intense pressure was applied to the other side, resulting, among other things in the creation of the new post of Prime Minister, with the objective of sidelining Arafat), the Iraq war policy has greatly assisted the terrorists in collecting new recruits. (It's true that bin Laden doesn't care about the Palestinian cause, or approve of secular nationalists like Arafat, but he still benefits from the general view that America is an agent of the oppression of the Palestinians).
Worse still, the desire for war with Iraq has led the Bush Administration to make political decisions not to go after terrorists, their backers and arms suppliers where the result might be inconvenient for the coalition of the willing. This was pretty clearly the case in relation to Pakistan and Saudi Arabia. In the case of Pakistan, the situation was already tricky enough. Between nuclear proliferation, the weakness and dubiousness of the regime and the near-certainty that bin Laden was hiding somewhere in the provinces and the need to secure support for, or at least acquiescence in, war with Iraq has meant that, until recently, little has been done on either front. The causes of the Administration's softness on Saudi Arabia are many and varied, but again, unwillingness to risk an open breach before the Iraq war was clearly important.
Finally, and most disgracefully of all, there is the case of Abu Musab Zarqawi, the terrorist most probably responsible for the Karbala atrocity a week or so ago. For well over a year after the S11 attacks, Zarqawi's group Ansar al-Islam was operating from a base inside the Kurdish controlled zone in Iraq, which was also part of the no-fly zone. The Pentagon drew up numerous plans for attacks on Zarqawi, but they were all vetoed on political grounds, according the NBC story linked here . There are various hypotheses about the precise grounds, all highly discreditable, but the most plausible is that a watertight plan would have required co-operation between US air forces, and Kurdish ground forces. This would have been most unpalatable to the Turkish government, which was being courted, up to the last minute, as a partner for the Iraq war. (Regular commentator Sebastian Holsclaw contributed part of this explanation, though he may well not like the way I've used it.) So nothing was done, and by the time the camp was attacked at the beginning of the war, Zarqawi and most of his followers were gone.
To sum up, the key element of the case against Blair, Aznar and Howard is not that they've stepped to the forefront of the war against terrorism when prudence would have dictated leaving the Americans to fight it by themselves. Rather it's that they've aided and abetted the Bush administration in its decision to use the war against terrorism as a pretext for settling old and unrelated scores, and that by doing so they've increased the danger facing both their own citizens and everyone else.