Is it possible that US spies pay off immigration officials in Khartoum/Tehran/Havana etc to supply them with a regular list of names of US citizens and foreigners who visit those countries ?
With today technology you do not need to do that. Every time your passport is scanned by immigration, your data goes into a data base and checked against various things Accessing this data base by the US can be voluntary ( Agreement between foreign services), or non-voluntary ( e.g scandal in Germany 2 years ago) .
When you board an Iran air flight today from Europe-Shengen ( or any other flight going to Iran, Syria or Iraq,) your get a separate immigration pre-boarding check which includes pass port scan. Same when you come back.
I would not bet much on believing this info stays firmly in the departure airport in the Country of boarding/arrival.
I am not at all a fan of this US anti-terrorist paranoia , but hey, in the end, if you want (or need) to go to the US you follow their rules or you stay home .