By David Sterman

(CNN) -- Last week, the American-backed Syrian Democratic Forces announced that it had taken Raqqa, the Syrian city, which had served as ISIS' capital. The taking of the city is the latest in a series of substantial military blows to ISIS' fortunes. However, Americans should not expect the fall of Raqqa to have a substantial effect on the jihadist threat at home.

The threat posed by ISIS to the United States has long come primarily from its ability to inspire and enable attacks -- and not from its territorial holdings in Syria and Iraq.

Since ISIS burst onto the global scene in 2014, seven individuals motivated by jihadist ideology have killed 74 people inside the United States in six attacks, according to New America's research. Though they may have been inspired by ISIS, none of those attacks were carried out under direct command by the group, and none of the deadly attacks involved a fighter who had returned from Syria or Iraq.

Nor are any of the perpetrators of the six deadly attacks known to have been enabled by ISIS via online communication with militants overseas. Although there have been non-lethal attacks and foiled plots in which the plotters communicated with ISIS militants abroad.

Even prior to ISIS, no deadly jihadist attacker inside the United States since 9/11 received formal militant training overseas or direction from a foreign terrorist organization, according to New America's research. This conclusion is supported not only by New America's data but by a National Counterterrorism Center report on Sunni violent extremist attacks in the United States since 9/11.

Six years into the Syrian civil war, there remains only one publicly known case of an American foreign fighter traveling to Syria, returning and plotting a terror attack inside the United States, according to New America's research. That fighter was associated with the al-Nusra Front -- not ISIS.

This is not to say that the fall of Raqqa and military successes more broadly in Syria and Iraq will have no positive effect on the threat to the homeland. The military success has allowed Syrian forces to retake territory that ISIS had used to train fighters and plot attacks in Europe and elsewhere, including potentially the United States.

It is also possible that the loss of Raqqa and ISIS' other military defeats will deal a propaganda blow by once again demonstrating how far it has fallen from its successful messaging strategy of 2014, when it was trumpeting its victories.

With territorial losses, ISIS may also find it more difficult to use the Internet to coach attackers. Even before the fall of Raqqa, coalition forces killed or captured numerous online recruiters who had aided plots in the West. Among them was Junaid Hussain, a British ISIS fighter, who communicated with the two men who opened fire outside a contest promoting the drawing of the prophet Mohammed in Garland, Texas, in May 2015, before he was killed by a security guard.

However, the extent to which ISIS' messaging was critical in driving the threat in the United States is unclear. Some attackers drew inspiration from jihadist groups other than ISIS and may have had non-jihadist motives as well. In the deadly December 2015 attack on military recruiting stations in Chattanooga, Tennessee, then-FBI Director James Comey confirmed the attacker was inspired by foreign terrorist propaganda, but warned that it was difficult to determine which group, in particular, inspired him.

According to a National Counterterrorism Center report, in another two deadly attacks -- the 2017 killing of a security guard in Denver and the 2014 killing of a worker at a meat packing plant in Oklahoma -- there is no intelligence community consensus regarding motive.

It is also far from clear that ISIS' communication online with plotters played a key role in driving the threat inside the United States. No deadly attacker is known to have received operational instruction online from a militant. John Mueller, a senior fellow at the CATO institute, has argued, based on a review of enabled plots, that online coaching of attackers "scarcely seems to be much of a game changer or a critical terrorist innovation."

Even if such enabled plotting does pose a substantial threat, online coaching can come from locations outside of Syria. Charges against a doctor located in the Philippines, for helping to plot and offering to fund -- via online communication -- an attack in the United States with a Canadian national and an American citizen living in Pakistan, were unsealed this October. The online correspondence between all three demonstrates the lack of restriction of such activity to ISIS' territory in Syria.

As the fall of Raqqa marks a significant turn in ISIS influence, we should remember that the terrorist threat within the United States today looks similar to the way it did prior to events in the Syrian city: attacks by individuals and pairs inspired by jihadist ideology or perhaps enabled by militants abroad. Addressing that challenge will take more than a military operation thousands of miles from home.