Bottom line? The threat is getting worse.
For instance, for the year 2013, the State Department estimated that terrorist attacks jumped more than 40 percent globally while RAND's Seth Jones asserted in The Wall Street Journal that the number of jihadists worldwide hovered around 100,000.
Those figures from last year are jaw-dropping - but from the looks of it, the situation isn't getting any better this year.
Let's start with Syria. What began as part of the peaceful "Arab Spring" movement against the dictator in Damascus, Bashar Assad, a few years ago has morphed into a violent "Islamist Spring" campaign that has set the country aflame.
The three-plus year civil war has emerged as an magnet for Islamist extremists from across the globe bent on joining the latest militant jihad.
Indeed, there may be some 12,000 foreign fighters from 80 countries in Syria, some of whom have joined up with al Qaeda-associated groups like the al Nusra Front and the Islamic State of Iraq and Syria, according to Bloomberg.
In addition to the bloodshed that has taken the lives of more than 150,000 people so far and displaced millions more, these foreign fighters are being schooled in the terrorist "dark arts" on the Syrian battlefield.
But it'd be a mistake to think the threat is simply "over there."
The director of National Intelligence has told Congress that al Qaeda terror groups in Syria have built camps to train "recruits" to return to their native lands and conduct attacks.
Bloomberg reports that 70 Americans and 3,000 Europeans have gone to Syria, presumably to fight alongside the extremists. The dread is that these fighters will come home undetected to carry out acts of terror.
That concern is justified.
Recently a young American reportedly participated in a truck bombing in Syria; possibly the first suicide attack by an American in that conflict.
Plus, recent European news accounts write of arrests related to Syria involving travel to Syria (Britain), recruiting foreign fighters for the conflict (Spain) or an attack by a Syrian jihad veteran (France/Belgium).
Besides the Americans who've traveled to Syria, many Europeans can come here without a visa, raising concerns terrorists might strike the homeland if they slip in undetected.
While Syria - which has the potential to become the next pre-9/11 Afghanistan - is arguably the biggest terror problem due to sheer numbers of violent extremists, we shouldn't overlook the carnage elsewhere.
Countries like Iraq, Pakistan, Afghanistan, Libya, Yemen, Nigeria, Somalia and their neighbors are also paying a big price in blood and treasure due to the spread of al Qaeda and other militant groups bent on imposing their will on others.
Assuming that these far-flung Islamist terror groups don't or won't put America, Americans or American interests in their crosshairs is a deeply dangerous mistake. Many already do - and more possibly will.
Peter Brookes is a Heritage Foundation senior fellow and a former deputy assistant secretary of defense.