The trouble is that every time the U.S. decides that international law doesn't apply, it sends a message to other countries like Russia that they can do likewise. It was an illegal war against Iraq and it violated the UN Charter. Only self-defence or if it is approved by as security council resolution can a nation legally use force. A resolution was never even brought forward because they knew France and Russia would veto it and probably China would have abstained.
General
Wesley Clark, the former Supreme NATO Allied Commander and Joint Chiefs of Staff Director of Strategy and Policy, describes in his 2003 book,
Winning Modern Wars, his conversation with a military officer in the Pentagon shortly after 9/11 regarding a plan to attack seven Middle Eastern countries in five years: "As I went back through the Pentagon in November 2001, one of the senior military staff officers had time for a chat. Yes, we were still on track for going against Iraq, he said. But there was more. This was being discussed as part of a five-year campaign plan, he said, and there were a total of seven countries, beginning with Iraq, then Syria, Lebanon, Libya, Iran, Somalia and Sudan."