I mean, so? Why should it matter where they are located?
It's the interpretation of some cloud providers that exchanging datagrams with entities in OFAC-sanctioned countries constitutes a prohibited transaction.
There's a big list of allowed Internet activity between the US and Iran.[2] It is explicitly US policy to not cut off Iran from the Internet. The State Department wants people in Iran to get info from the outside world. However, the US does not allow US domain registrations or web hosting "for or on behalf of the Government of Iran".
The Office of Foreign Assets Control can be queried for case by case info. That's appropriate here.
[1] https://www.ecfr.gov/current/title-31/subtitle-B/chapter-V/p...
[2] https://www.ecfr.gov/current/title-31/subtitle-B/chapter-V/p...