The F117 is a very stealthy plane, given its geometry (flat panels). Yet a 1960s radar with essentially no digital equipment took it out, largely using human intelligence and guerrilla tactics.
Iran has modern digital electronics (to improve the signal to noise ratio, merge different data sources, etc) and modern electronics. They are also master guerrilla fighters and have, great, native missile technology.
Iranian airspace is contested at best. We certainly do not have air superiority over it.