Other than Iraq, what wars has the US bypassed the UN for?

yes, but that's kind of sketchy. it doesn't specifically authorize military action but some could argue that it wasn't needed as it was "self defense." not saying i agree with it, but i think we can all agree that the war in afghanistan isn't really a good example of ROGUE US WARS IN SPITE OF THE UN, like iraq could be.

also

On December 20, 2001, the UNSC did authorize the creation of an International Security Assistance Force (ISAF) with authority to take all measures necessary to fulfill its mandate of assisting the Afghan Interim Authority in maintaining security.[31] Command of the ISAF passed to NATO on August 11, 2003.

so the un did take an active role in operation enduring freedom, which one could also argue is a defacto show of support!