Courtesy of OFAC, these places are generally off limits:
Belarus, Burma, as well as Cote D’Ivoire (Ivory Coast), Cuba, the Democratic Republic of Congo, Iran, Iraq, Liberia, North Korea, Sudan, Syria, and Zimbabwe
You can't touch these people or companies either no matter what:
Nope. If you violate OFAC as a foreigner you are shit-listed by the US government. You become radioactive and anybody with even the most remote ties to the United States can't do business with you safely. The US government can find a random rule from their massive trove to use to throw the book at you at that point. You're in their crosshairs both literally and figuratively since there is a decades long precedent of US extrajudicial killings of even its own citizens. They will go to immense lengths to shut you down if they hate you enough. The extradition of Kim Dotcom has been going on for a decade and they tried to put him in prison for life because he once had a server in the United States. That's the entire legal basis for the extradition. If they fail he is bankrupted, if they succeed he will be in an American prison until he dies.
OFAC violations can have numerous painful impacts on a foreign company’s business beyond mere payment of fines, including triggering red flags during due diligence by prospective partners, investors, acquirors, and financiers, putting companies in breach of contractual obligations to their banks, creating a disadvantage or disqualification in bidding for contracts, and attracting additional scrutiny from the Committee on Foreign Investment in the United States (CFIUS) when attempting to acquire or invest in U.S. businesses.
US government overreach is hard to overstate. If things get bad enough the FBI/CIA will attempt to abduct you (Viktor Bout, Assange, Snowden) or suicide you in a foreign prison (John McAfee). Most likely nobody will learn about your story after your unfortunate "suicide."
Belarus, Burma, as well as Cote D’Ivoire (Ivory Coast), Cuba, the Democratic Republic of Congo, Iran, Iraq, Liberia, North Korea, Sudan, Syria, and Zimbabwe
You can't touch these people or companies either no matter what:
https://www.treasury.gov/ofac/downloads/consolidated/consoli...
The amount of stuff you are prohibited from doing business with is huge: https://home.treasury.gov/policy-issues/office-of-foreign-as...