Iraq

There were allegations that Iraq had weapons of mass destruction and considering that Iraq famously used weapons of mass destruction during the Iran-Iraq War, such an allegation was not preposterous.

The UN doesn't do much anymore after the result of their structure in the Security Council and their poor reactions to events in Iraq

Iraq did not go to war with the US. Iraq did invade Kuwait in 1991, and there was a UN response of which the US was the leading contributor. Then the US went back to Iraq again, in 2002, because of concern about noncompliance with UN security council resolutions and weapons inspections. Iraq never declared war on the US, although it is possible to argue that their actions were provocative.

The headquarters of the UN Security Council resides in New York City. Further main offices of the UN Security Council are also found in Geneva, Vienna, and Nairobi.