If there's something more imminent than a U.S. action in Syria, it's that the UN investigation, once again, will be dismissed as an auxiliary and fruitless attempt by the U.S. in the face of conflict. Despite vocalization by the Obama administration for coordination and support of a UN investigation, the UN investigation into chemical weapon use is now nothing close to a factor in the U.S. policy toward Syria. Here's how the U.S./UN relationship hasn't changed since Iraq.
Critics of the Iraq war point to the all-too-brief WMD investigation by UN inspector Hans Blix as a dismissal by the Bush administration of the role of the UN in intervention conflicts. In that particular case, Blix's report that Saddam Hussein didn't have WMDs directly opposed U.S. intelligence reports. Ultimately, no WMD's were found. Clearly, the Bush administration had disregarded the role of the UN when U.S. forces invaded Iraq.
After Obama's election, it was assumed by many that the U.S. would respect the UN more. However, the U.S./UN relationship hasn't changed dramatically. While Secretary of State John Kerry urged Syrian cooperation for UN investigators, and had hoped for a UN resolution previously, National Security Advisor Susan Rice quickly dispelled the aura of permission and contemplation.
Rice told the U.S. ambassador the UN, Samantha Power, "The investigation is … too late, and will actually tell us what we already know: CW (chemical weapons) was used. It won't even tell us by whom, which we already know." At some point after, the White House sent private communications to the UN to remove their inspectors, heavily hinting at military strikes.
Seeing as Secretary of Defense Chuck Hagel has already announced that U.S. military forces are ready to engage in whatever necessary action is possible, and British and French officials have met with Obama. It's clear that something will be happening, and that the UN has little to say about it. Rice's line about "what we already know" has already pointed to classified intelligence gatherings before any UN investigation.
Why doesn't the U.S. care about the UN in escalating conflict situations? Well, one can look to the more infamous failings of the UN for some obvious answers. After investigations, the UN may want to merely deploy peacekeepers, who have notoriously faltered in Rwanda and Bosnia. They could urge other actors, which would likely be the U.S. anyways. During Sri Lanka's vicious civil war against the Liberation Tigers of Tamil Eelam, for over two decades the UN acknowledged appalling conditions but wouldn't intervene. Also, Russia has that pesky veto power on the Security Council.
Then there's the argument specific to the U.S.: UN actions aren't always in U.S. interests. (Gasp!) Between Al-Qaeda, support of Iran, and ties to Russia, the U.S. has an interest in Syria beyond human rights. If an UN investigation is just going to drag on the bureaucracy of international politics and hinder U.S. interests, why wait for them?
Kerry's initial promotion of the UN investigation was a courtesy. When it comes down to it, the U.S. is going to do what the U.S. is going to do, regardless of the UN.
Cue UN jokes from 2003.