"Diplomatic credibility" has nothing to do with convincing tyrants of anything. It has to do with convincing the rest of the world that the United States has a credible strategy, based upon sound facts and intelligence, to contain the proliferation of nuclear weapons among tyrant states.

We had convinced the world (UN) regarding Iraq. All the western intelligence services shared the same conclusions regarding WMD. Ninteen UN resolutions were ignored by Iraq. Inspection teams were periodically ejected. It was clear as Tom contends that Europe could only deal in diplomacy, however failed. Action, however necessary, is abhorent to their moribund culture.

By running off at the mouth half-cocked about WMDs that didn't exist we've tanked any possibility of advancing any strategy effective at containing the spread of nuclear weapons.

See above re: WMDs and others' shared opinions at the time.
So by your flawed thinking, Europe facing a nuclear threat no matter how iminent will disregard any strategy proposed by the US because we all were wrong regarding WMD and only the US, UK, Australia and Poland had the sack to act on it. Uh huh.