"If the french hadn't said in advance they would veto a resolution authorizing the use of force against Iraq, then, the day the resolution would have been voted, they would have vetoed it and I don't see what difference it would have made."

I guess from that perspective we should be appreciative, but either you don't understand that members don't keep their vote secert until they actually vote- that there is a huge amount of discussion and negotiation about a resolution before putting something to a vote. Or you think the french were simply being too nice, and should have deceived the US as to how they were planning to vote on a specific resolution, so they could have a opportuny "embarrass" by US pretending they were going vote for french negotiated resolution- say with 5 month delay, then defeating "their" resolution with a veto.

"It's true the press knew that when Bush sent all the troops in the neighbouring Arab countries, it also deduced the US was going to invade Iraq, no matter what happened at the Security Council. It would have been too humiliating for Bush to withdraw without invading."

Well, yes and no. To send troops there, to pass 1441, and to have Saddam continue to not comply with the cease fire agreement. And then to decide to pack up the troops and go home. Yes that would be humiliating to the US and UK. It would also fundemently change our relationship with Kuwait, SA, and other Arab countries. But before doing something that stupid, we might choose some other course of action- I don't know what would be, but probably something could have been fiqured out that would in some way mitigated this.
There of course was only one reason to put +100,000 troops in that theater. It's purpose was to change Saddam's regime. Of course, Saddam had the option of changing his regime. He could have actually decided to comply with the cease fire agreement. He could have stepped down and put some other family member in power. He could said, I'm going to change this country- I'm going to hold a real election! There are numerous things Saddam could have done, he could solved this problem 10 years prior.

"It was child's play for the French to humiliate the US at the Security Council after Powell's february 5th 2003 presentation as they knew the US had no real evidence to show the world. But it also hurt the French more then they admit it."

I think you are missing the big picture. Yes, Powell was humiliated, I'm sure the french could have manage if they tried really hard could have hurt Powell so badly that he would need to step down. The big picture was the middle east and world relationships in general. The UN as an institution wasn't really that important in this context.