>Powell’s speech did not help the credibility of the US.

That is revisionist, and 100% incorrect. Bush did not have much credibility on the world stage or even at home. Powell did. When he co-signed what Bush and the other warmongers were saying, the public became willing to accept the necessity of the war.

I vividly remember the speech and the absolute difference it made in most people's minds about the pending invasion, not just globally but among the US general public as well. He was one of the few people with credibility on both sides of the aisle and on the world stage.