Following the attacks of September 11 (2001), the US response in invading Afghanistan was widely regarded by other countries as thoughtful, constrained and appropriate. Al-Qaeda had trained thousands of its followers in camps in Afghanistan, and the Taliban rulers of that country had supported and been supported by bin Laden. Allies did help the USA in Afghanistan.
The military operation in Iraq, in March 2003, was another matter. Whatever the merits or otherwise, it was a period of incompetent diplomacy and dirty politics on all sides which led to divisions across the Atlantic and within Europe. Even within nations, opinions were divided and not necessarily along political lines. The United States was impatient for decisive action; the United Kingdom wanted UN authority for military action; Germany and France led the call for more time for the inspection process. The US and UK opted to use UNSCR 1441, and previous resolutions on Iraq, as their authority for military action.
This failure of diplomacy has had a series of unfortunate consequences. In the USA, antipathy towards the UN has been reinforced. Although unexpected countries like Canada and Mexico had taken a tough stand in the Security Council, the real anger was directed at France and Germany. Yet the embryonic EU common foreign and security policy mechanism could do little to paper over the wide division between its members. Governments (if not their people) in UK, Spain, Italy, Denmark and Portugal were strongly supportive of the US push for military action. At the end of January 2003, their leaders, together with those of Hungary, the Czech Republic and Poland, signed a joint note for the Wall Street Journal expressing their unity. France, Germany, and Belgium were strongly against a rush to war. In a more complex set of divisions, the prospective new members of the EU were brought into the dispute. This gave rise to Defense Secretary Donald Rumsfeld's unfortunate characterisation of a division between "Old Europe", represented by France and Germany, and "New Europe" drawn from grateful eastern European states. President Chirac added fuel to the flames by suggesting that pro-US candidate countries were "badly brought up", and hinting that their EU membership applications might need reviewing.
The diplomatic machinations over Iraq were also bruising for NATO. Afghanistan had shown the future: the US expects to lead coalitions of the willing. In any event, there would have been little chance of consensus among member states over mounting a NATO operation. Even with a sidelined role, the divisions between the various national players managed to cause excitement. NATO found itself in difficulties over authorisation for planning for the defence of Turkey in the event of a conflict in Iraq. The diplomatic temperature rose as France, Germany and Belgium saw themselves being pressured into giving a stamp of approval for US early moves on Iraq. To general surprise, Turkey in the end did not allow ground operations to be launched against Iraq from its territory. There were no attacks by Iraq on Turkey. Nevertheless, the concern in NATO was real, and the public name calling between members was undoubtedly damaging.