You can be sure that the US Senate got their information from US Military and intelligence sources. I'm asking the source for a good reason: what's the more likely scenario?
A) The US invades Iraq and suddenly tens of thousands fly there (not the US) to do their bombings and beheadings.
or
B) The US ends a dictatorship that kept the 65% Shiia majority down and there's civil war, which includes bombings and beheadings, and the US Military declares it to be Al-Queda to give soldiers the idea that they're "fighting evil" rather than just killing the people that live there.