There is some nuance here. While some "sanctions" may not be applicable, the United States has a concept called deemed export, where exposing a non-US Person (~non-citizen with no green card) to technologies in the US, for example during the course of regular employment, can be problematic. Depending on the foreign citizen's nationality, the level of exposure that is deemed problematic can vary. For Iranian citizens, it is basically almost everything unless open-source. This is why all FANGs regularly apply for a deemed export license before commencing employment of foreign individuals with problematic nationalities.
There is some nuance here. While some "sanctions" may not be applicable, the United States has a concept called deemed export, where exposing a non-US Person (~non-citizen with no green card) to technologies in the US, for example during the course of regular employment, can be problematic. Depending on the foreign citizen's nationality, the level of exposure that is deemed problematic can vary. For Iranian citizens, it is basically almost everything unless open-source. This is why all FANGs regularly apply for a deemed export license before commencing employment of foreign individuals with problematic nationalities.