U.S. officials appear to be on alert for retaliation from Iran after striking the country’s nuclear facilities on Saturday. Donald Trump’s administration is especially concerned about Iranian sleeper cells, also known as terrorists who could plan attacks from within the U.S., NewsNation reported. “Intelligence services in the U.S. are working overtime to contend and mitigate risks and threats that can emerge on its domestic soil. The more protracted this conflict goes on, the heightened risk for both U.S. forces and assets in the Middle East, but also to U.S. security domestically,” Barak Seener, a senior fellow at the Henry Jackson Society, told NewsNation. What are sleeper cells composed of? Sleeper cells could be comprised of people living in the U.S. who are quietly living normal lives while preparing to commit acts of terrorism at any moment. Per The Independent , U.S. officials said the FBI is monitoring these threats closely as the country’s tension with Iran continues to...