The way you are using these words seems to indicate you might be confused about how this works.
The US has not "sanctioned" LetsEncrypt or ISRG. The US sanctions foreign entities as punishment for various reasons precisely because they are not subject to US law. That's the entire point of leveraging a sanction -- to pressure those outside of your legal jurisdiction. If they were in your jurisdiction, you'd simply arrest them.
People and organizations basically anywhere not permitted to do business with anyone your country has sanctioned. Anyone who does business internationally should be aware of their country's sanctioned list. That applies no matter where you live on the planet.
The US has not "sanctioned" LetsEncrypt or ISRG. The US sanctions foreign entities as punishment for various reasons precisely because they are not subject to US law. That's the entire point of leveraging a sanction -- to pressure those outside of your legal jurisdiction. If they were in your jurisdiction, you'd simply arrest them.
People and organizations basically anywhere not permitted to do business with anyone your country has sanctioned. Anyone who does business internationally should be aware of their country's sanctioned list. That applies no matter where you live on the planet.