The US did not have approval at the UN, don't you remember the lies that Colin Powell presented, pictures of mobile nuclear weapons systems that didn't exist!!!! Don't you remember the lies for going in? Bush said there were weapons of mass destruction. The UN didn't believe either one of them that's why they would not give support for the invasion. They had to lie since the American people never would have approved the invasion.
Since there was no approval for invasion by the UN, Bush made up the term "coalition of the willing", in other words those that the US bribed to help the US inavade Iraq.
By the way, who gave us authority to invade Afghanistan and Pakistan? Both are soverign nations, and those incursions are violations of international law.