https://en.wikipedia.org/wiki/Coalition_of_the_willing_(Iraq...
You see Eastern European countries who were grateful for NATO expansion or wanted future NATO membership. You see the UK and Australia which always follow the US. There are a couple of wildcards line Spain, Denmark and Italy.
Germany and France are absent and there was huge criticism of the Iraq invasion at the time.
In general, the whole EU was much more critical of the US in the 2000s than it was in 2020-2024. The current criticism is mostly Trump related and not fundamental. To summarize, in the 2000s the EU had an independent foreign policy which is now completely gone. How that evolved exactly is interesting. Has the US played off the Eastern European countries against heretics like France and Germany to achieve this goal? Is it a symptom of the international elites moving in lockstep?