Step 1:
Write down the actual reason for invading Iraq. Call it variable A (for "Actual").
Step 2:
Write down the reason given for the invasion (no reason given after the invasion counts). Call it variable B (for "Bush").
Step 3:
Compare variables A and B. If they are not the same, you've been misled.
It's really that simple.
Extra Credit:
If A <> B
1: decide if you would trust a random person after they mislead you on such a scale
2: decide if you trust Bush after pushing through a deception on this scale and
3: explain your answers.