Katie Pavlich

As the extremely radical terror group the Islamic State, better known as ISIS, continues its march on Iraq and mass slaughter of Christians, many are asking the question: Will ISIS strike inside the United States?

According to experts, and ISIS itself, it's a possibility and steps must be taken immediately to prevent it. More from CNN:

Within hours of U.S. military jets and drones conducting a strike on ISIS artillery that had been used against Kurdish forces defending Irbil, ISIS supporters called for retaliatory attacks against the United States.

"It is a clear message that the war is against Islam and the mujahideen. The mujahideen must strive and seek to execute proactive operations in their own home, America, to discipline America and its criminal soldiers," Abu al-Ayna al-Khorasani, an administrator of Shumukh al-Islam, the top-tier forum for ISIS propaganda, wrote on his account Friday, according to a translation by the SITE Intelligence group.

Other ISIS supporters railed against the United States using the Twitter handle #AmessagefromISIStoUS, posting images of the wreckage of the twin towers. "Don't forget 11 Sept .. Maybe US citizens want more like that," one extremist tweeted. In June after ISIS captured Mosul, its supporters had warned against strikes in a Twitter campaign #CalamityWillBefallUS.

One major concern is homegrown U.S. fighters currently overseas in Syria of Iraq coming back home on U.S. passports to carry out attacks. Just two weeks ago we saw American Moner Mohammad Abu-Salha of Florida carry out a suicide attack in Syria after first returning home to the U.S. for a visit. Before executing his suicide mission overseas, he directly threatened the U.S. and said, "We are coming for you."

A new video released by Al Qaeda-linked fighters in Syria allegedly shows 22-year-old Moner Mohammad Abu-Salha ripping up his American passport and chewing parts of it before setting it on fire.

In May, Moner Mohammad Abu-Salha became the first known American to carry out a suicide bomb attack in Syria's civil war when he detonated a truckload of explosives in an effort to kill Syrian troops.

And before he blew himself up, Abu-Salha had returned to the United States for months following training with Syrian Islamic militants.

Meanwhile, pro-ISIS allies are taunting President Obama directly and apparently hung this flag outside of the White House late last week.

Last week, an ISIS leader proclaimed to VICE News the terror group will raise the "flag of Allah" above the White House and called the United States cowards for sending drones instead of soldiers to fight them.

"I say to America that the Islamic Caliphate has been established. And we will not stop. Don’t be cowards and attack us with drones. Instead send your soldiers, the ones we humiliated in Iraq. We will humiliate them everywhere, God willing, and we will raise the flag of Allah in the White House," said in a video report by VICE.

ISIS has quickly and forcefully proven they are not the "JV team" the White House recently classified them to be.

Currently, there are no updated terror alters from Homeland Security's National Terrorism Advisory System.

Katie Pavlich

Katie Pavlich is the Editor at Townhall.com. Follow her on Twitter @katiepavlich. She is a New York Times Best Selling author. Her latest book Assault and Flattery: The Truth About the Left and Their War on Women, was published on July 8, 2014.