The National Review online has this article discussing the current state of US/Iran reporting.   A previous blog entry quoted an Iranian woman who also deplored the sorry state of journalism in this area.

[In Iran] Public hangings and stonings are now routine (funny, isn't it, that half the world gets upset at the prospect of a stoning of a single Nigerian woman, but nobody says "boo" about repeated stonings in Iran);

...Meanwhile, street fighting continues all over the country, and seven members of the regime's militia were killed in a gunfight near the Iraqi border.

All this will no doubt surprise most Americans, because events inside Iran are not reported in our leading media. It has now been over a year since the monster demonstrations in the streets of Tehran (dismissed as "soccer riots" by the few reporters who have brought themselves to report them at all), and for the past several months there have been many stories noting the intimate relations between leading terrorist groups and the Islamic Republic.

His point about the press Nigeria receives vs. Iran is particularly important.   I think there are 2 factors at play here.

• Relative perceived legitimacy of the 2 governments.   Like many Europeans (who, BTW are also deeply implicated in supporting Iran), many members of the US press believe in One Nation, One Vote-- that the act of being declared a nation automatically entitles one to a certain level of respect.   Nigeria's "nationhood" was never as loudly proclaimed in the press as Iran's.
• "Established" national religions are a far more taboo press topic than religiously "influenced" polices within a seemingly secular state.