To have the slightest hope of answering this question, you need to do enough homework to rid yourself of the amazingly inaccurate and easily disproved media narrative on Iraq. That narrative, which matches the liberal narrative, goes something like this:
George Bush took his eye off the ball when he invaded Iraq. Instead of concentrating on Afghanistan, where the real terrorists were and when they are now resurgent, he invaded Iraq, which had no WMDs and no ties to al Qaeda. This served to embolden radical Islamic terrorists by handing them a propaganda victory of historic proportions (it was, in fact, a "cause celeb" for jihadists), and [*] it resulted in a predictable civil war between Sunnis and Shiites, who have hated each other for centuries. Some al Qaeda terrorists came to Iraq after the invasion, but "al Qaeda in Iraq" (AQI) was largely a homegrown resistance force that never amounted to a significant part of the insurgency anyway. We need to withdraw our troops from Iraq, leaving a few to target the sprinkling of al Qaeda terrorists we attracted there, and concentrate on the fight in Afghanistan. That's where the real terrorists are.
I have placed an asterisk where the standard media narrative goes seriously astray. It's true that Saddam (not Bush) lied about having WMDs. He didn't have any of significance, and he deliberately misled the world into believing that he did. If you are angrily trapped in the "Bush lied!" quagmire, you should dig yourself out of it and go investigate for yourself why Saddam misled the world even when the U.S. had 200,000 troops massed on his border. The truth is vastly more interesting than the "Bush lied!" fantasy. But that's another story. The idea that Saddam was not yet a WMD threat when we invaded is hard to argue with. His relationship with radical Islamic terrorists is a lot more complicated, and it's ludicrous to suggest that he had no ties with them at all, but it is also probably the case that those ties were not as extensive as intelligence analysts imagined they were. Finally, the invasion of Iraq really was, for a time, a "cause celeb" for jihadists around the world. I doubt anyone would deny that. In fact, you'd have to be as misguided about Iraq as leading Democrats are to believe that the U.S. invasion did not attract jihadists like flies.
The standard narrative veers far from the truth where I have placed the asterisk. Anyone with the slightest intellectual curiosity about what went wrong in Iraq (and what is now going right) can easily figure out for themselves that al Qaeda has completely ignored Afghanistan while absolutely wreaking havoc in Iraq. This is a fact (not an opinion) that you need to understand before you can seriously inquire into what al Qaeda would have been doing for the last 5 years had the U.S. not invaded Iraq. Thus, before reading any further, I recommend that you educate yourself on this matter. The key to understanding the problem with the standard media narrative is hiding in plain view and has to do with the suicide bombers of Iraq and Afghanistan. If you believe that I am merely a neocon propaganda machine, then go investigate for yourself what is known about them. And then be amazed by what you discover. What you'll discover is that the suicide bombers of Iraq are almost all foreigners funneled in Iraq by al Qaeda to kill Shiite civilians (not to kill American troops) in order to provoke the Shiite militias into killing Sunnis. That was how al Qaeda decided it could topple the fledgling government of Iraq and send demoralized American forces home in ignominious defeat. Al Qaeda's suicide bombers have killed more than 10,000 Iraqis over the years. Nearly 4000 Iraqi civilians were killed by suicide bombers in 2007 alone. Al Qaeda finally succeeded in bringing the Mahdi Army into the battle by bombing the Golden Mosque in Samarra in early 2006, and, in response, that Shiite militia probably killed 30,000 Sunnis in Baghdad alone. But it is important to keep in mind that they were deliberately provoked into doing so by al Qaeda, so, in a very real way, al Qaeda gets the credit for these deaths as well.
Not one word of this is debatable, but it is a little complicated, so surface-scratching reporters are not going to get it across to anyone. You have to dig into the details for yourself. When you do, you'll see that everything I say is true even though leading Democrats have denied it from day one. To them, AQI was an exaggerated neocon conspiracy theory. In reality (to them), al Qaeda was resurgent in Afghanistan because Bush "took his eye off the ball." To find out if the Democrats are right about this, go investigate for yourself what the suicide bombers of Afghanistan have been doing over the last 5 years. Please do that before forming a strong opinion on the matter. What you will discover is that (a) the suicide bombers of Afghanistan are a bunch of bumbling incompetents from Pakistan who only manage to kill themselves most of the time and (b) they have killed fewer people in 5 years than AQI killed every coupe of months in Iraq (before AQI was a spent force, that is). The reason is that al Qaeda has completely ignored Afghanistan over the last 5 years while they have concentrated everything they had in a now failed effort to achieve victory in Iraq. What was, for a time, a "cause celeb" for jihadists has become a propaganda catastrophe for al Qaeda's global mission.
If you believe otherwise, ask yourself: what actual evidence do we have that al Qaeda is active in Afghanistan? The suicide bombers are doing next to nothing in that country (you can easily determine this for yourself), but perhaps al Qaeda's global leadership is there. If so, perhaps we occasionally use a Predator drone in Afghanistan to take out a high ranking al Qaeda figure. That would certainly be evidence that al Qaeda's leadership is in Afghanistan. But it never, ever happens. What often happens is that those Predator drones take out al Qaeda leadership in Pakistan (here's an example). This is really important to understand. The Democrats often try to obscure the critical distinction between Afghanistan and Pakistan by talking about the fact that al Qaeda's leadership is flourishing along the Afghanistan/Pakistan border. In truth, al Qaeda's leadership is located inside Pakistan. Once you realize that, and once you add in the fact that suicide bombers of Afghanistan consist of relatively non-lethal bumbling incompetents organized by the Taliban (not by al Qaeda), then you are finally in a position to ask what al Qaeda would have been doing these last 5 years had we not invaded Iraq.
What would al Qaeda have been doing in recent years had we not invaded Iraq? A clear understanding of what actually happened over the last 5 years pretty much answers the question. If U.S. forces were not desecrating Muslim territory in Iraq but were instead only desecrating Muslim territory in Afghanistan, is it very hard for you to figure out what the jihadist "cause celeb" would have been? Obviously, al Qaeda's foreign suicide bombers would have been funnelled into Afghanistan instead of Iraq. Their game plan would have differed because there are not enough Shiites there to be worth killing, but suicide bombings in Afghanistan would have been vastly more frequent and vastly more deadly. High ranking politicians, Afghan army and police (including their high ranking officials), and NATO soldiers would have been relentlessly targeted. In short, Afghanistan would be an absolute mess, and it would have been caused by the same force that instead chose to turn Iraq into the mess it once was.
Imagine that scenario, and now add in the facts that (a) our invasion of Afghanistan was not approved by the UN and was illegal under international law (did you realize that?), and (b) theories abounded that the true purpose of the invasion of Afghanistan to facilitate the building of a major oil pipeline. You don't hear much about the illegal nature of the invasion or the "blood-for-oil" nonsense with respect to Afghanistan only because we achieved victory there so quickly. But those talking points would be front-and-center today had al Qaeda seriously opposed us there. But they never did, and my point for today is that they obviously would have had we not invaded Iraq. One way or another, we were going to have that war with al Qaeda. As it happens, we fought the war against them in Iraq (because they chose that battlefield), and we turned the tables by inflicting an ignominious defeat on them. In so doing, we disconfirmed the world's most dangerous theory, which is that America is a paper tiger with a powerful military that need not be feared. We came closer to confirming that theory than I ever thought possible in this post-9/11 world when the Democrats took control of Congress and were on a mission to withdraw our troops from Iraq. In the end, the Democrats failed, and al Qaeda has suffered accordingly.

