Your question is always illogical which is why you don't get an answer that satisfies you. Where would terrorists be if they weren't in Iraq? I don't know and neither do you. You however are claiming you do know.
It's the old excluded middle trick again. You give only two alternatives, that the terrorists are in Iraq and might be in the US instead. By doing this you exclude all the other information about what might have happened and where they might be instead to try and prove a point which is utter rubbish.
All those terrorists, whatever that means is a combination of Iraqis fighting an occupation, Baathists, Syrians, Saudi Arabians, a thousand other types and some Al Quaeda in there somewhere.
The implication is that the Al Quaeda would be in the US if they weren't in Iraq. All intelligence seems to indicate there are few to no Al Quaeda in Iraq and they are making bombs in other places like Turkey and Saudi Arabia for example.
Your main point is insinuating that Al Quaeda is in Iraq and is leaving the rest of the world alone, which is factually untrue in every part and relies on knowledge of Al Quaeda which you don't have anyway.
Now to that excluded middle tossed aside by you. What would happen if the Baathists and Saddam supporters weren't in Iraq? Well they weren't restricted to Iraq before the invasion and they weren't causing trouble then. Anything they did now outside Iraq (assuming they could get out) would be because of the war. If they could get out would they attack people outside Iraq instead of the troops in Iraq? Possibly but the only reason to do that would be to perhaps take hostages or blow up buildings in protest. They can do that more easily in Iraq now but they may change in the future.
What would the Syrians and Saudi Arabians do if they weren't in Iraq? Intelligence suggests few are in iraq anyway but before the war they would have been doing what they used to do, which was next to nothing. Since Syrians and Saudi Arabians can travel freely through much of the world I would assume that since they are not really doing anything elsewhere then the so called flypaper in Iraq just incited them to violence they wouldn't have committed otherwise.
And of course the innocent farmers and clerks in Iraq didn't just suddenly rise up by themselves. Another excluded middle raises its head. Some farmers have relatives and friends killed and want revenge. Some no doubt are Baathists and are either afraid of or welcome Saddam coming back and help for that reason.
Some farmers no doubt just hate foreigners and want them to leave. Some probably are religious and think foreign troops in Iraq mean jihad is needed.
So the answer is if you exclude all the actual facts and cherry pick the slivers of doubtful information that suits your bias you can make a case. The technique was used by Rumsfeld and Cheney in the same way. Unfortunately sophistry (arguments with logical flaws) usually fail, as they have so spectacularly in Iraq.
I suppose this must seem like an empty post to you since it's all about the excluded middle you refuse to believe exists. Still facts have a way of dominating things even if you pretend they don't exist.