Bush most likely never said that Iraq was directly involved in 9/11. However, here is an article
http://www.cnn.com/2004/ALLPOLITICS/06/17/Bush.alqaeda/ where he says the following things:
"The reason I keep insisting that there was a relationship between Iraq and Saddam and al Qaeda, because there was a relationship between Iraq and al Qaeda."
and
Bush reiterated that the administration never said that "the 9/11 attacks were orchestrated" between Saddam Hussein and al Qaeda. "We did say there were numerous contacts between Saddam Hussein and al Qaeda,"
Al Qaeda is the group that carried out the 9/11 attacks. He tells us that Iraq is friends with Al Qaeda. It doesn't take a rocket scientist to see what he is trying to do here. Most people don't pay much attention to the world around them. Here is a line directly from the BBC in regards to one of Bush's statements about saddam not being involved with 9/11. "The comments - among his most explicit so far on the issue - come after a recent opinion poll found that nearly 70% of Americans believed the Iraqi leader was personally involved in the attacks. "
It's not hard to see the pattern here.
-Bush takes office.
-Bush has always wanted to invade Iraq.
-9/11 happens
-Al Qaeda is named as those behind the attacks
-We invade Afghanistan where Bin Ladin and his crew are hiding.
-Now is a prime to time remove Saddam from power.
-Bush then starts to sell the public on Iraq. He tells everyone they have weapons of mass destruction and ties to Al Qaeda. The public - many of who can't even find Iraq on a map - immediately assume that this means Saddam was involved in 9/11. It's not much of a hard sell.