Former House Speaker Kevin McCarthy, R-Calif., is sounding alarms as the FBI places its counterterrorism teams on high alert, warning Democrats that stalling funding for the Department of Homeland Security (DHS) could carry serious national security consequences."If there is some type of attack within America, it is going to be on the Democrats who faulted by not funding DHS during this critical time and allowing the border to be open during [the Biden administration]," McCarthy told "The Sunday Briefing.""If I was a Democrat – I usually don't like to give them advice, but this is too critical for the security of America – go back to Washington, fund DHS now," he said.McCarthy's comments came Sunday, as American counterterrorism agencies quietly monitored suspected sleeper cells on U.S. soil in the wake of joint U.S.–Israel strikes on Iran.GOP WARNS DEMOCRATS' DHS SHUTDOWN COULD JEOPARDIZE WORLD CUP SECURITYThe strikes resulted in the death of Iran’s Supreme Leader Ayatollah Ali Khamenei and several senior Iranian officials.The offensive measure also led to the U.S. adversary vowing retaliation and a myriad of warnings from security experts like former assistant FBI Director Chris Swecker, who told Fox News, "If ever there's going to have a Hezbollah cell or a Hamas cell act in the United States in a violent way, it's now."The FBI said a mass shooting in Austin, Texas, that left three people dead, including the shooter, and 14 others injured early Sunday is being investigated as a potential act of terrorism.DHS FUNDING STALEMATE THAWS AS WHITE HOUSE SENDS DEMOCRATS 'SERIOUS' COUNTEROFFERFederal law enforcement sources told Fox News the suspect, a 53-year-old naturalized U.S. citizen who was born in Senegal, was wearing clothing that said "Allah" on it and an undershirt featuring an Iranian flag.McCarthy criticized Democrats' push for a vote on War Powers resolutions as a "very stupid play" as DHS funding remains stalled."Here's the Democrats, who first voted to fund DHS and then voted against the exact same bill where it shut down. So the Coast Guard – it's not being funded [neither are] the Secret Service [nor] the TSA…" he said.McCarthy urged Democrats to "do your job" and "protect Americans in their homeland."Fox News' Amanda Macias, Michael Dorgan, Bill Melugin, Brooke Taylor and Mitch Picasso contributed to this report.