While Iran’s military might not present what U.S. military planners refer to as a pressing or major-power, near-peer kind of threat, the country’s existing force is nevertheless taken quite seriously at the Pentagon for a number of reasons. After all, Iran has an emerging nuclear weapons threat, regional territorial ambitions, support and funding for anti-U.S. terrorist groups, alliances or cooperative relationships with U.S. adversaries and conducts overt maneuvers to intimidate or threaten safe maritime passage in the Strait of Hormuz.
Clearly, any successful military campaign against Iran would of course rely almost entirely upon an ability to quickly achieve air superiority, something which would require the destruction of Russian-built S-300 and S-400 air defenses. These weapons, of course depending upon the extent to which they have been modernized, present very serious threats as they are increasingly networked with faster digital processors, wider radar apertures and much longer ranges. 
One immediate factor might be the F-35 stealth fighter jet, simply because any kind of air supremacy would first need to be established before a fourth-generation aircraft or less stealthy airplanes to strike. The F-35 jet might prove to be a particularly relevant choice given that the Russian-built S-400 missile system is road-mobile and can therefore easily reposition. A high altitude bomber, while likely fully undetectable, might greatly benefit from the lower altitude, yet still stealthy, highly maneuverable F-35 jet able to track and shoot down moving air defense targets. The combination of speed, computer processing and sensor range and fidelity give the F-35 jet a unique and potentially unparalleled ability to destroy a mobile S-400 missile system. More at link, of course. A lot of big words, for a civil engineer.
So, just who is this author? Wikipedia sez -
Kris Osborn (born May 16, 1969) is a journalist, military expert, and former news anchor. He worked at CNN Headline News from 2001 to 2004 as an anchor, and specialized in military issues. He has worked as a reporter for KSTP-TV in Minneapolis and a correspondent for Entertainment Tonight. He has written articles for the Washington Times and reported for KO NewsMachine, an independent news-content company. He has appeared as an expert military guest on MSNBC and Fox News.
Nice resume. A "military expert" because he says he is.