Monday’s precarious ceasefire reduced tensions between Israel and Iran, but the government’s highest authorities warn the risk of Americans suffering attacks from pro-Iranian terrorists on their own streets may not disappear so quickly — and experts say the Biden-Harris administration’s four-year-long indifference to border security may have allowed sleeper cells to hide themselves within “a wave of mass immigration.”

The Department of Homeland Security (DHS) has issued a national terrorism advisory declaring that the U.S. military involvement in the Israeli-Iranian conflict gave Americans a greater threat of becoming the targets of anti-American terrorists everywhere in the world — including inside the United States.

“The ongoing Iran conflict is causing a heightened threat environment in the United States,” said the DHS. “The likelihood of violent extremists in the Homeland independently mobilizing to violence in response to the conflict would likely increase if Iranian leadership issued a religious ruling calling for retaliatory violence against targets in the Homeland. Multiple recent Homeland terrorist attacks have been motivated by anti-Semitic or anti-Israel sentiment, and the ongoing Israel-Iran conflict could contribute to US-based individuals plotting additional attacks.”

Operation Midnight Hammer, the June 21 mission in which U.S. bombers targeted three Iranian nuclear facilities, could “motivate violent extremists and hate crime perpetrators seeking to attack targets perceived to be Jewish, pro-Israel, or linked to the US government or military in the Homeland,” said the DHS warning, issued Sunday. The terror advisory, which lasts until September 22, also warned of cyber attacks from the Iranian government or “pro-Iranian hacktivists.”

Hours before President Donald Trump announced Tehran and Tel Aviv had accepted a framework bringing an end to the 12-day war, Iran launched Operation Fatah’s Blessing, a largely symbolic missile strike aimed at the U.S. Al Udeid air base in Qatar. U.S. officials said Iran tipped them off ahead of the attack, which inflicted no casualties.

But the longer-term threat may come from terrorists living in the shadows of American society. U.S. experts say, and Iranian officials threaten, that anti-American sleeper cells have likely burrowed into the American interior years ahead of the Middle East’s latest conflict, taking advantage of lax border enforcement to establish a fifth column inside the “Great Satan.”

NBC News reported Iran sent President Trump a communiqué at last week’s G7 summit in Canada vowing to activate sleeper cells inside the United States in retaliation for any strike on the Iranian homeland. “The Iranian nation cannot be subdued,” said Ayatollah Ali Khamenei last Wednesday. “Americans must know that any U.S. military intervention will undoubtedly be met with irreparable harm.”

Border Patrol agents estimate roughly 10 million illegal border crossings took place — more than the population of 41 states — during the Biden-Harris administration. Immigration officials released about half of the Iranians they apprehended at the border — admitting 729 of the 1,504 Iranian nationals they encountered during the 2021 to 2024 fiscal years. Border Czar Tom Homan put the number of Iranians the previous administration let out through its catch-and-release policy at 1,272.

Neither figure includes the number of Iranian terrorists who may have blended into the two million known gotaways who slipped into the United States without being interrogated.

The newly confirmed commissioner of U.S. Customs and Border Protection (CBP), Rodney Scott, confirmed in a memo Saturday the threat posed to U.S. citizens by terrorist sleeper cells has “never been higher.”

“The dangers increased significantly during the four years of open-border policies under the Biden administration,” Ira Mehlman, media director at the Federation for American Immigration Reform (FAIR), told The Washington Stand. “Those who took the extra trouble and paid extra to the smugglers to help them elude border enforcement agents had good reasons for not wanting to be encountered. We must assume that among the gotaways are people who have ties to terrorist groups.”

“Even some who were encountered and released into the country were later found to have ties to terrorist groups, and others may have made it through, because they were not on any watch lists,” Mehlman, who has repeatedly highlighted the possibility terrorists would exploit America’s porous border, noted. “Given the events of the past few days, there is every reason to believe that the Iranian regime will look for ways to strike back against the U.S. and we should assume that the sleeper cells that Commissioner Scott has warned about will be part of that retaliation. Therefore, it is essential that DHS use whatever resources they have available to identify and track down these cells and step up security around likely targets.”

The sheer number of immigrants, legal and illegal, make it easier for malign foreign elements to blend into the landscape, experts say.

“A very small percentage of people coming to the United States intend to do us harm. When the numbers reach historic levels, however, you inevitably increase the odds of something tragic taking place,” Jeremy Beck, co-president of Numbers USA, told TWS. The presence of growing Islamic communities in every major metropolitan area could provide areas for sleeper cells to disappear unnoticed — until it is too late.

Naturalized U.S. citizens and second-generation Americans have also been known to become radicalized and attack their homeland.

“Millions of those inadmissible aliens remain in the U.S. today,” Beck warned. “A credible immigration system would ensure that they return to their home nations, relieve overwhelmed Americans communities, and make it more difficult for bad actors to disappear amidst a wave of mass immigration.”